Showing 1–50 of 168 results for author: Jiang, L

Integer Linear Programming Decoder for Abelian and Non-Abelian Topological Codes

Authors: Dian Jing, Aubrey Zhang, Liang Jiang, Ruben Verresen

Abstract: Topological orders (TOs) are widely used as quantum error-correcting codes, with anyon excitations serving as error syndromes. For certain Abelian TOs, decoding can be performed by independently matching particle-antiparticle pairs of each species. However, matching-based decoders cannot handle more general fusion rules in either Abelian or non-Abelian TOs, nor account for noise that correlates di… ▽ More Topological orders (TOs) are widely used as quantum error-correcting codes, with anyon excitations serving as error syndromes. For certain Abelian TOs, decoding can be performed by independently matching particle-antiparticle pairs of each species. However, matching-based decoders cannot handle more general fusion rules in either Abelian or non-Abelian TOs, nor account for noise that correlates different anyon species. While clustering decoders are more broadly applicable, they typically neglect anyon data and fusion properties, leading to poor performance in practice. In this work, we introduce a fundamentally different decoder for arbitrary TOs based on integer linear programming (ILP). The ILP formulation linearizes the error-correction problem through the introduction of auxiliary variables and encodes fusion rules as linear constraints. Classical optimization then identifies the minimum-weight error configuration. As concrete examples, we determine error-correction thresholds for three TOs: the Abelian $\mathbb{Z}_2$ TO under depolarizing noise, where charge and flux errors are correlated; the Abelian $\mathbb{Z}_3$ TO, which does not admit a pairwise matching decoder; and the non-Abelian $D_4$ TO under noise channels that generate all anyon species. We demonstrate the versatility of the ILP decoder by showing a clear performance advantage over most existing decoders in all three cases. We further extend the method to incorporate noisy syndrome measurements and propose a just-in-time variant for continuous error correction. Our results establish ILP as a natural framework for handling correlated errors and general anyon fusion rules, and as a powerful and flexible general-purpose decoder for incoherent anyon noise in arbitrary TOs, with applications to fault-tolerant quantum computation. △ Less

Submitted 19 August, 2026; originally announced August 2026.

Oval-shaped resonance distortion as a signature of quasiparticle heating effect in a niobium superconducting resonator

Authors: Zhenyuan Sun, Genting Dai, Xiao Geng, Liangliang Yang, Mingjun Cheng, Qing Yu, Jinlin Chang, Yi Yang, Linpan Jiang, Jianshe Liu, Wei Chen

Abstract: We investigate the nonlinear behavior of a superconducting microwave resonator subjected to a dissipative mechanism where the associated quality factor (Q factor) decreases with increasing dissipated power, leading to a dissipative feedback effect. By modifying the Rothwarf-Taylor equations, we establish a macroscopic quasiparticle heating (QPH) model that directly links the quality factor to the… ▽ More We investigate the nonlinear behavior of a superconducting microwave resonator subjected to a dissipative mechanism where the associated quality factor (Q factor) decreases with increasing dissipated power, leading to a dissipative feedback effect. By modifying the Rothwarf-Taylor equations, we establish a macroscopic quasiparticle heating (QPH) model that directly links the quality factor to the microwave readout power. The key finding is the identification of a distinctive oval-shaped distortion in the resonance circle in the complex plane. This distortion serves as a practical experimental signature for identifying the readout power regime in which QPH dominates the loss, under conditions where other nonlinear mechanisms are sufficiently weak. To validate the model, we design and fabricate a niobium (Nb) half-wavelength coplanar waveguide (CPW) resonator and conduct systematic bath temperature and readout power sweeps. The model provides a well fit to the observed oval-shaped resonance circle distortion across a wide range of operating conditions, confirming the QPH mechanism as the primary source of the dissipative non-linearity in the parameter space investigated. △ Less

Submitted 20 July, 2026; originally announced July 2026.

Experimental Realization of Synthetic Magnonic Lattice via Floquet Engineering

Authors: Amin Pishehvar, Jayakrishnan M. P. Nair, Zhaoyou Wang, Zixin Yan, Yu Jiang, Liang Jiang, Benedetta Flebus, Xufeng Zhang

Abstract: Magnonic systems, which exploit spin-wave excitations in magnetic materials, offer a promising platform for coherent information processing due to their low dissipation, strong nonlinearities, and intrinsic nonreciprocity. However, scaling magnonic circuits remains challenging, particularly with low-loss insulators such as yttrium iron garnet (YIG), which are difficult to pattern. Here, we experim… ▽ More Magnonic systems, which exploit spin-wave excitations in magnetic materials, offer a promising platform for coherent information processing due to their low dissipation, strong nonlinearities, and intrinsic nonreciprocity. However, scaling magnonic circuits remains challenging, particularly with low-loss insulators such as yttrium iron garnet (YIG), which are difficult to pattern. Here, we experimentally realize a synthetic dimension in a magnonic system by coupling multimode magnon resonances in the frequency domain using time-periodic Floquet modulation. This approach enables electronically tunable interactions between discrete modes within a single YIG device, forming a reconfigurable mode-space lattice that supports functionalities such as Bloch oscillation. Our results demonstrate that high-dimensional magnonic dynamics can be achieved without increasing device footprint, establishing synthetic dimensions as a scalable and programmable route for integrated magnonic technologies. This advancement positions magnonic systems as promising platforms for engineering emergent phenomena that are inaccessible at equilibrium. △ Less

Submitted 29 June, 2026; originally announced June 2026.

Comments: 16 pages, 6 figures

Journal ref: Phys. Rev. Lett. 137, 046706 (2026)

A Neuroevolution Potential for Gallium Oxide: Accurate and Efficient Modeling of Polymorphism and Swift Heavy-Ion Irradiation

Authors: Yaohui Gu, Binbo Li, Lingyang Jiang, Yuhui Hu, Wenqiang Liu, Lijun Xu, Pengfei Zhai, Jie Liu, Jinglai Duan

Abstract: Gallium oxide (Ga2O3) is a wide-bandgap semiconductor with promising applications in high-power and high-frequency electronics. However, its complex polymorphic nature poses substantial challenges for fundamental studies, particularly in understanding phase-transformation behaviors under nonequilibrium conditions. Here, we develop a robust, accurate, and computationally efficient machine-learning… ▽ More Gallium oxide (Ga2O3) is a wide-bandgap semiconductor with promising applications in high-power and high-frequency electronics. However, its complex polymorphic nature poses substantial challenges for fundamental studies, particularly in understanding phase-transformation behaviors under nonequilibrium conditions. Here, we develop a robust, accurate, and computationally efficient machine-learning interatomic potential (MLIP) for Ga2O3 based on the neuroevolution potential (NEP) framework combined with an energy-dependent weighting strategy. The resulting NEP potential demonstrates clear advantages over the state-of-the-art tabGAP potential with respect to both accuracy and computational efficiency. Furthermore, we introduce a physically process-oriented sampling strategy to systematically augment the training dataset, thereby enhancing the MLIP performance for targeted physical phenomena. As a representative application, a dedicated NEP potential is constructed for swift heavy-ion (SHI) irradiation simulations of \b{eta}-Ga2O3. The simulated results are in quantitative agreement with experimental observations and provide a consistent physical explanation for the reported experimental discrepancies regarding phase transformations in the ion track of \b{eta}-Ga2O3. △ Less

Submitted 20 May, 2026; v1 submitted 15 January, 2026; originally announced January 2026.

Comments: 13 pages, 9 figures

Scattering Problem in Bose-Einstein Condensates with Magnetic Domain Wall

Authors: Mei Zhao, Lijia Jiang, Tao Yang, Jun-Hui Zheng

Abstract: We present a comprehensive theoretical study of linear wave scattering from magnetic domain walls with varied twist angles $Θ$ in spin-$1/2$ Bose-Einstein condensates (BECs). Using a gauge transformation, we show that scattering observables depend solely on the total twist $Θ$, independent of chirality. Within the Bogoliubov-de Gennes (BdG) framework, we develop a transfer-matrix method to compute… ▽ More We present a comprehensive theoretical study of linear wave scattering from magnetic domain walls with varied twist angles $Θ$ in spin-$1/2$ Bose-Einstein condensates (BECs). Using a gauge transformation, we show that scattering observables depend solely on the total twist $Θ$, independent of chirality. Within the Bogoliubov-de Gennes (BdG) framework, we develop a transfer-matrix method to compute reflection and transmission coefficients for incident phonons and free particles. Our results reveal a scattering threshold at the Zeeman energy $E = \hbarΩ_0$, separating a pure phonon regime from multi-channel scattering involving both collective and single-particle excitations above threshold. For large twist angles, competition between kinetic and Zeeman energies reduces the effective spin rotation, leading to comb-like density modulations and Fano-like resonances below threshold. The transition probability between phonon and particle channels is strongly tunable with $Θ$, enhanced for odd multiples of $π$ but suppressed for even multiples. These findings establish twist-engineered domain walls as a versatile platform for controlling quantum transport, with implications for atomtronic devices and quantum simulation. △ Less

Submitted 8 April, 2026; v1 submitted 19 December, 2025; originally announced December 2025.

Comments: 11 pages, 8 figures

Classically Sampling Noisy Quantum Circuits in Quasi-Polynomial Time under Approximate Markovianity

Authors: Yifan F. Zhang, Su-un Lee, Liang Jiang, Sarang Gopalakrishnan

Abstract: While quantum computing can accomplish tasks that are classically intractable, the presence of noise may destroy this advantage in the absence of fault tolerance. In this work, we present a classical algorithm that runs in $n^{\rm{polylog}(n)}$ time for simulating quantum circuits under local depolarizing noise, thereby ruling out their quantum advantage in these settings. Our algorithm leverages… ▽ More While quantum computing can accomplish tasks that are classically intractable, the presence of noise may destroy this advantage in the absence of fault tolerance. In this work, we present a classical algorithm that runs in $n^{\rm{polylog}(n)}$ time for simulating quantum circuits under local depolarizing noise, thereby ruling out their quantum advantage in these settings. Our algorithm leverages a property called approximate Markovianity to sequentially sample from the measurement outcome distribution of noisy circuits. We establish approximate Markovianity in a broad range of circuits: (1) we prove that it holds for any circuit when the noise rate exceeds a constant threshold, and (2) we provide strong analytical and numerical evidence that it holds for random quantum circuits subject to any constant noise rate. These regimes include previously known classically simulable cases as well as new ones, such as shallow random circuits without anticoncentration, where prior algorithms fail. Taken together, our results significantly extend the boundary of classical simulability and suggest that noise generically enforces approximate Markovianity and classical simulability, thereby highlighting the limitation of noisy quantum circuits in demonstrating quantum advantage. △ Less

Submitted 7 October, 2025; originally announced October 2025.

Comments: 32 pages, 7 figures + X inline figures

Intrinsic Heralding and Optimal Decoders for Non-Abelian Topological Order

Authors: Dian Jing, Pablo Sala, Liang Jiang, Ruben Verresen

Abstract: Topological order (TO) provides a natural platform for storing and manipulating quantum information. However, its stability to noise has only been systematically understood for Abelian TOs. In this work, we exploit the non-deterministic fusion of non-Abelian anyons to inform active error correction and design decoders where the fusion products, instead of flag qubits, herald the noise. This intrin… ▽ More Topological order (TO) provides a natural platform for storing and manipulating quantum information. However, its stability to noise has only been systematically understood for Abelian TOs. In this work, we exploit the non-deterministic fusion of non-Abelian anyons to inform active error correction and design decoders where the fusion products, instead of flag qubits, herald the noise. This intrinsic heralding enhances thresholds over those of Abelian counterparts when noise is dominated by a single non-Abelian anyon type. Furthermore, we use Bayesian inference to obtain a statistical mechanics model for fixed-point non-Abelian TOs with perfect measurements under any noise model, which yields the optimal threshold conditioned on measuring anyon syndromes. We numerically illustrate these results for $D_4 \cong \mathbb Z_4 \rtimes \mathbb Z_2$ TO. In particular, for non-Abelian charge noise and perfect syndrome measurement, we find a conditioned optimal threshold $p_c=0.218(1)$, whereas an intrinsically heralded minimal-weight perfect-matching (MWPM) decoder already gives $p_c=0.20842(2)$, outperforming standard MWPM with $p_c = 0.15860(1)$. Our work highlights how non-Abelian properties can enhance stability, rather than reduce it, and discusses potential generalizations for achieving fault tolerance. △ Less

Submitted 27 October, 2025; v1 submitted 31 July, 2025; originally announced July 2025.

Journal ref: Phys. Rev. Lett. 136, 120405 (2026)

Index Theorem and Vortex Kinetics in Bose-Einstein Condensates on a Haldane Sphere with a Magnetic Monopole

Authors: Xi-Yu Chen, Lijia Jiang, Tao Yang, Jun-Hui Zheng

Abstract: The geometry-gauge interplay constitutes a fundamental issue in quantum physics, with profound implications spanning from quantum gravity to topological matter. Here, we investigate the dynamic effects of geometry-gauge interplay in Bose-Einstein condensates (BECs) on a Haldane sphere with a magnetic monopole. We reveal an index theorem that establishes a correspondence between BEC vortices and th… ▽ More The geometry-gauge interplay constitutes a fundamental issue in quantum physics, with profound implications spanning from quantum gravity to topological matter. Here, we investigate the dynamic effects of geometry-gauge interplay in Bose-Einstein condensates (BECs) on a Haldane sphere with a magnetic monopole. We reveal an index theorem that establishes a correspondence between BEC vortices and the topology of the gauge field, enabling the construction of vortex-monopole composites. Furthermore, we derive the universal logarithmic interaction between composites, which governs the structure of the ground-state vortex lattice. By developing a kinetic theory, we predict scale-invariant vortex dynamics and an emergent duality. Both are confirmed through numerical simulations. This work first presents the dynamical coupling mechanism between spatial geometry and gauge fields, providing deep insights into superfluid systems with topological gauge structures in curved space. △ Less

Submitted 4 July, 2025; originally announced July 2025.

Comments: 10 pages, 3 figures

Impact of border defects on the magnetic flux penetration in superconducting films

Authors: Alejandro V. Silhanek, Lu Jiang, Cun Xue, Benoît Vanderheyden

Abstract: Defects in superconducting systems are ubiquitous and nearly unavoidable. They can vary in nature, geometry, and size, ranging from microscopic-size defects such as dislocations, grain boundaries, twin planes, and oxygen vacancies, to macroscopic-size defects such as segregations, indentations, contamination, cracks, or voids. Irrespective of their type, defects perturb the otherwise laminar flow… ▽ More Defects in superconducting systems are ubiquitous and nearly unavoidable. They can vary in nature, geometry, and size, ranging from microscopic-size defects such as dislocations, grain boundaries, twin planes, and oxygen vacancies, to macroscopic-size defects such as segregations, indentations, contamination, cracks, or voids. Irrespective of their type, defects perturb the otherwise laminar flow of electric current, forcing it to deviate from its path. In the best-case scenario, the associated perturbation can be damped within a distance of the order of the size of the defect if the rigidity of the superconducting state, characterized by the creep exponent $n$, is low. In most cases, however, this perturbation spans macroscopic distances covering the entire superconducting sample and thus dramatically influences the response of the system. In this work, we review the current state of theoretical understanding and experimental evidence on the modification of magnetic flux patterns in superconductors by border defects, including the influence of their geometry, temperature, and applied magnetic field. We scrutinize and contrast the picture emerging from a continuous media standpoint, i.e. ignoring the granularity imposed by the vortex quantization, with that provided by a phenomenological approach dictated by the vortex dynamics. In addition, we discuss the influence of border indentations on the nucleation of thermomagnetic instabilities. Assessing the impact of surface and border defects is of utmost importance for all superconducting technologies, including superconducting resonators, superconducting single-photon detectors, superconducting radio-frequency cavities and accelerators, superconducting cables, superconducting metamaterials, superconducting diodes, and many others. △ Less

Submitted 5 June, 2025; originally announced June 2025.

Comments: 36 pages, 24 figures, 281 references

Journal ref: Appl. Phys. Rev. 12, 041324 (2025)

Direct Joule-Heated Non-Equilibrium Synthesis Enables High Performing Thermoelectrics

Authors: Chenguang Zhang, Jose Recatala-Gomez, Zainul Aabdin, Yi Jiang, Luyang Jiang, Sze Yu Tan, Hong Liu, Yuting Qian, Coryl Jing Jun Lee, Sabrine Hachmioune, Vaishali Taneja, Anqi Sng, Pawan Kumar, Haiwen Dai, Zhiqian Lin, Weng Weei Tjiu, Fengxia Wei, Qianhong She, D. V. Maheswar Repaka, David Scanlon, Kanishka Biswas, Yee Kan Koh, Kedar Hippalgaonkar

Abstract: High-throughput synthesis of bulk inorganic materials is crucial for accelerating functional materials discovery but is hindered by slow, energy-intensive solid-state methods. We introduce Direct Joule-Heated Synthesis (DJS), a rapid, single-step and scalable solid-state synthesis technique achieving a $10^5$-fold speedup and 20,000x energy efficiency improvement over conventional synthesis. DJS e… ▽ More High-throughput synthesis of bulk inorganic materials is crucial for accelerating functional materials discovery but is hindered by slow, energy-intensive solid-state methods. We introduce Direct Joule-Heated Synthesis (DJS), a rapid, single-step and scalable solid-state synthesis technique achieving a $10^5$-fold speedup and 20,000x energy efficiency improvement over conventional synthesis. DJS enables the synthesis of dense, bulk chalcogenides ($\mathrm{Bi_{0.5}Sb_{1.5}Te_3}$, $\mathrm{AgSbTe_2}$), achieving a zT of 2.3 at 573 K in optimally Cd/Se co-doped $\mathrm{AgSbTe_2}$, one of the highest for polycrystalline materials at this temperature. DJS enables optimal co-doping and rapid, non-equilibrium solidification, producing lamellar microstructures, interfacial regions, and cation-ordered nanodomains that scatter all-scale phonons, achieving ultralow lattice thermal conductivity (~0.2 $W m^{-1} K^{-1}$ at 573 K). DJS establishes a new benchmark for scalable and fast synthesis, accelerating functional material discovery. △ Less

Submitted 4 June, 2025; originally announced June 2025.

Electrically tunable quantum interference of atomic spins on surfaces

Authors: Hao Wang, Jing Chen, Peng Fan, Yelko del Castillo, Alejandro Ferrón, Lili Jiang, Zilong Wu, Shijie Li, Hong-Jun Gao, Heng Fan, Joaquín Fernández-Rossier, Kai Yang

Abstract: Controlling quantum interference near avoided energy-level crossings is crucial for fast and reliable coherent manipulation in quantum information processing. However, achieving tunable quantum interference in atomically-precise engineered structures remains challenging. Here, we demonstrate electrical control of quantum interference using atomic spins on an insulating film in a scanning tunneling… ▽ More Controlling quantum interference near avoided energy-level crossings is crucial for fast and reliable coherent manipulation in quantum information processing. However, achieving tunable quantum interference in atomically-precise engineered structures remains challenging. Here, we demonstrate electrical control of quantum interference using atomic spins on an insulating film in a scanning tunneling microscope. Using bias voltages applied across the tunnel junction, we modulate the atomically-confined magnetic interaction between the probe tip and surface atoms with a strong electric field, and drive the spin state rapidly through the energy-level anticrossing. This all-electrical manipulation allows us to achieve Landau-Zener-Stückelberg-Majorana (LZSM) interferometry on both single spins and pairs of interacting spins. The LZSM pattern exhibits multiphoton resonances, and its asymmetry suggests that the spin dynamics is influenced by spin-transfer torque of tunneling electrons. Multi-level LZSM spectra measured on coupled spins with tunable interactions show distinct interference patterns depending on their many-body energy landscapes. These results open new avenues for all-electrical quantum manipulation in spin-based quantum processors in the strongly driven regime. △ Less

Submitted 1 June, 2025; originally announced June 2025.

Journal ref: Nature Communications 16, 8988 (2025)

Resonance-enhanced Floquet cavity electromagnonics

Authors: Amin Pishehvar, Zixin Yan, Zhaoyou Wang, Yu Jiang, Yizhong Huang, Josep M. Jornet, Liang Jiang, Xufeng Zhang

Abstract: Floquet engineering has been recently recognized as an important tool for manipulating the coherent magnon-photon interaction in cavity electromagnonics systems at microwave frequencies. In spite of the novel hybrid magnonic functionalities that have been demonstrated, the effect of the Floquet drive has been relatively weak due to the limited driving efficiency, limiting its broader application.… ▽ More Floquet engineering has been recently recognized as an important tool for manipulating the coherent magnon-photon interaction in cavity electromagnonics systems at microwave frequencies. In spite of the novel hybrid magnonic functionalities that have been demonstrated, the effect of the Floquet drive has been relatively weak due to the limited driving efficiency, limiting its broader application. This work shows that by utilizing LC resonances, the Floquet drive in our cavity electromagnonic device can be drastically enhanced, giving rise to drastically boosted interaction between hybrid modes with fundamentally different spectral characteristics compared with previous demonstrations. In addition, the Floquet drives can also be obtained from GHz signals on such a system, allowing the demonstration of more advanced signal operations. Our novel resonance-enhanced Floquet cavity electromagnonics points to a new direction to fully unleash the potential of Floquet hybrid magnonics. △ Less

Submitted 23 May, 2025; originally announced May 2025.

Comments: 10 pages, 7 figures

Combined effect of incentives and coupling in multigames in two-layer networks

Authors: Luo-Luo Jiang, Yi-Ming Li, Wen-Jing Li, Attila Szolnoki

Abstract: The lack of cooperation can easily result in inequality among members of a society, which provides an increasing gap between individual incomes. To tackle this issue, we introduce an incentive mechanism based on individual strategies and incomes, wherein a portion of the income from defectors is allocated to reward low-income cooperators, aiming to enhance cooperation by improving the equitable di… ▽ More The lack of cooperation can easily result in inequality among members of a society, which provides an increasing gap between individual incomes. To tackle this issue, we introduce an incentive mechanism based on individual strategies and incomes, wherein a portion of the income from defectors is allocated to reward low-income cooperators, aiming to enhance cooperation by improving the equitable distribution of wealth across the entire population. Moreover, previous research has typically employed network structures or game mechanisms characterized by homogeneity. In this study, we present a network framework that more accurately reflects real-world conditions, where agents are engaged in multiple games, including prisoner's dilemma games in the top-layer and public good games in the down-layer networks. Within this framework, we introduce the concept of ``external coupling'' which connects agents across different networks as acquaintances, thereby facilitating access to shared datasets. Our results indicate that the combined positive effects of external coupling and incentive mechanism lead to optimal cooperation rates and lower Gini coefficients, demonstrating a negative correlation between cooperation and inequality. From a micro-level perspective, this phenomenon primarily arises from the regular network, whereas suboptimal outcomes are observed within the scale-free network. These observations help to give a deeper insight into the interplay between cooperation and wealth disparity in evolutionary games in large populations. △ Less

Submitted 13 January, 2025; originally announced January 2025.

Comments: 17 pages, 7 figures, accepted for publication in Journal of Physics: Complexity

Journal ref: J. Phys. Complex. 6 (2025) 015003

Guidelines for Correlative Imaging and Analysis of Reactive Lithium Metal Battery Materials

Authors: Shuang Bai, Zhao Liu, Diyi Cheng, Bingyu Lu, Nestor J. Zaluzec, Ganesh Raghavendran, Shen Wang, Thomas S. Marchese, Brandon van Leer, Letian Li, Lin Jiang, Adam Stokes, Joseph P. Cline, Rachel Osmundsen, Paul Barends, Alexander Bright, Minghao Zhang, Ying Shirley Meng

Abstract: To unlock the full potential of lithium metal batteries, a deep understanding of lithium metal reactivity and its solid electrolyte interphase is essential. Correlative imaging, combining focused ion beam and electron microscopy offers a powerful approach for multi-scale characterization. However, the extreme reactivity of lithium metal and its SEI presents challenges in investigating deposition a… ▽ More To unlock the full potential of lithium metal batteries, a deep understanding of lithium metal reactivity and its solid electrolyte interphase is essential. Correlative imaging, combining focused ion beam and electron microscopy offers a powerful approach for multi-scale characterization. However, the extreme reactivity of lithium metal and its SEI presents challenges in investigating deposition and stripping mechanisms. In this work, we systematically evaluated the storage stability of lithium metal in glovebox before and after electrochemical deposition. We then assessed different FIB ion sources for their impact on lithium metal lamella preparation for transmission electron microscopy. Furthermore, we examined cryogenic-TEM transfer methods, optimizing for minimal contamination during sample handling. Contrary to prior assumptions, we demonstrate that high resolution imaging of pure lithium metal at room temperature is achievable using inert gas transfer with an electron dose rate exceeding 1000 e/A2/s, without significant detectable damage. In contrast, SEI components, such as Li2CO3 and LiF display much greater sensitivity to electron beams, requiring cryogenic conditions and precise dose control for nano/atomic scale imaging. We quantified electron dose limits for these SEI components to track their structural evolution under irradiation. Based on these findings, we propose a robust protocol for lithium metal sample handling - from storage to atomic-level characterization - minimizing damage and contamination. This work paves the way for more accurate and reproducible studies, accelerating the development of next-generation lithium metal batteries by ensuing the preservation of native material properties during analysis. △ Less

Submitted 26 December, 2024; originally announced December 2024.

Comments: 31 pages, 6 figures

On-Demand Magnon Resonance Isolation in Cavity Magnonics

Authors: Amin Pishehvar, Zhaoyou Wang, Yujie Zhu, Yu Jiang, Zixin Yan, Fangxin Li, Josep M. Jornet, Jia-Mian Hu, Liang Jiang, Xufeng Zhang

Abstract: Cavity magnonics is a promising field focusing the interaction between spin waves (magnons) and other types of signals. In cavity magnonics, the function of isolating magnons from the cavity to allow signal storage and processing fully in the magnonic domain is highly desired, but its realization is often hindered by the lack of necessary tunability on the interaction. This work shows that by util… ▽ More Cavity magnonics is a promising field focusing the interaction between spin waves (magnons) and other types of signals. In cavity magnonics, the function of isolating magnons from the cavity to allow signal storage and processing fully in the magnonic domain is highly desired, but its realization is often hindered by the lack of necessary tunability on the interaction. This work shows that by utilizing the collective mode of two YIG spheres and adopting Floquet engineering, magnonic signals can be switched on-demand to a magnon dark mode that is protected from the environment, enabling a variety of manipulation over the magnon dynamics. Our demonstration can be scaled up to systems with an array of magnonic resonators, paving the way for large-scale programmable hybrid magnonic circuits. △ Less

Submitted 20 December, 2024; originally announced December 2024.

Comments: 19 pages, 7 figures

Quantum-data-driven dynamical transition in quantum learning

Authors: Bingzhi Zhang, Junyu Liu, Liang Jiang, Quntao Zhuang

Abstract: Quantum neural networks, parameterized quantum circuits optimized under a specific cost function, provide a paradigm for achieving near-term quantum advantage in quantum information processing. Understanding QNN training dynamics is crucial for optimizing their performance, however, the role of quantum data in training for supervised learning such as classification and regression remains unclear.… ▽ More Quantum neural networks, parameterized quantum circuits optimized under a specific cost function, provide a paradigm for achieving near-term quantum advantage in quantum information processing. Understanding QNN training dynamics is crucial for optimizing their performance, however, the role of quantum data in training for supervised learning such as classification and regression remains unclear. We reveal a quantum-data-driven dynamical transition where the target values and data determine the convergence of the training. Through analytical classification over the fixed points of the dynamical equation, we reveal a comprehensive `phase diagram' featuring seven distinct dynamics originating from a bifurcation with multiple codimension. Perturbative analyses identify both exponential and polynomial convergence class. We provide a non-perturbative theory to explain the transition via generalized restricted Haar ensemble. The analytical results are confirmed with numerical simulations and experimentation on IBM quantum devices. Our findings provide guidance on constructing the cost function to accelerate convergence in QNN training. △ Less

Submitted 10 August, 2025; v1 submitted 2 October, 2024; originally announced October 2024.

Comments: 17+28 pages, 25 figures

Journal ref: npj Quantum Information 11, 132 (2025)

Anisotropic spin filtering by an altermagnetic barrier in magnetic tunnel junctions

Authors: Boyuan Chi, Leina Jiang, Yu Zhu, Guoqiang Yu, Caihua Wan, Xiufeng Han

Abstract: The spin filtering effect, distinct decaying lengths experienced by oppositely spin-polarized electrons in a magnetic barrier, generally occurs in ferromagnetic (FM) insulators or semiconductors. With the rise of altermagnetic (ALM) materials which exhibit similar capability of spin-polarizing electrons with ferromagnets, it is a nature question whether the ALM insulators or semiconductors can als… ▽ More The spin filtering effect, distinct decaying lengths experienced by oppositely spin-polarized electrons in a magnetic barrier, generally occurs in ferromagnetic (FM) insulators or semiconductors. With the rise of altermagnetic (ALM) materials which exhibit similar capability of spin-polarizing electrons with ferromagnets, it is a nature question whether the ALM insulators or semiconductors can also act as unique barriers for the spin splitting effect. Here, through first-principles calculations, we investigated the complex band structure of the ALM insulator FeF$_2$ and found that it possesses an anisotropic spin filtering effect: along the [001] direction of FeF$_2$, a current remains spin-neutral but has locally nonvanishing spin polarizations in the momentum space; moreover, along the [110] direction of FeF$_2$, a current will be globally spin-polarized by different attenuation lengths of oppositely spin-polarized electrons. Leveraging this anisotropic spin filtering effect, we designed two types of MTJs with the ALM barrier: ALM electrode/ALM insulator barrier/non-magnetic (NM) electrode and FM electrode/ALM insulator barrier/NM electrode, using RuO$_2$(001)/FeF$_2$/IrO$_2$ and CrO$_2$(110)/FeF$_2$/IrO$_2$ as the corresponding prototypes, respectively. We found that these two proposed MTJs exhibited the tunneling magnetoresistance (TMR) ratios of 216\% and 3956\%, by matching the conduction channels of the electrodes and the spin-resolved lowest decay rate of the barrier in the momentum space. Our work deepens and generalizes understanding toward the spin filtering effect for the rising ALM insulators and semiconductors, and broadens applications of the AFM spintronics. △ Less

Submitted 5 September, 2024; originally announced September 2024.

Comments: 6 pages, 4 figures

Synthetic half-integer magnetic monopole and single-vortex dynamics in spherical Bose-Einstein condensates

Authors: Xi-Yu Chen, Lijia Jiang, Wen-Kai Bai, Tao Yang, Jun-Hui Zheng

Abstract: Magnetic monopoles are crucial in explaining the quantization of electric charges and quantum Hall effects, while artificially creating a minimal magnetic monopole in experiments remains a challenge. Here, we come up with a flexible way to simulate a half-integer-type monopole in Bose gases and investigate the induced vortex dynamics on a sphere. We list the possible experiment parameter settings… ▽ More Magnetic monopoles are crucial in explaining the quantization of electric charges and quantum Hall effects, while artificially creating a minimal magnetic monopole in experiments remains a challenge. Here, we come up with a flexible way to simulate a half-integer-type monopole in Bose gases and investigate the induced vortex dynamics on a sphere. We list the possible experiment parameter settings for different isotopes and discuss their experimental feasibility. With the assumption of a rigid monopole-vortex structure, we analytically predict the vortex trajectory in an external magnetic field. We then confirm the result by numerically solving the Gross-Pitaevskii equation, which employs two gauges simultaneously (the Wu-Yang approach) to prevent singularity in the one-gauge method when a monopole is present. The study offers significant insight into the characteristics of monopoles and vortices, facilitating avenues for experimental validation. △ Less

Submitted 19 March, 2025; v1 submitted 29 July, 2024; originally announced July 2024.

Comments: 11 pages, 4 figures, 1 table

Journal ref: Phys. Rev. A 111, 033322 (2025)

Optimization of noncollinear magnetic ordering temperature in Y-type hexaferrite by machine learning

Authors: Yonghong Li, Jing Zhang, Linfeng Jiang, Long Zhang, Yugang Zhang, Xueliang Wu, Yisheng Chai, Xiaoyuan Zhou, Zizhen Zhou

Abstract: Searching the optimal doping compositions of the Y-type hexaferrite Ba2Mg2Fe12O22 remains a long-standing challenge for enhanced non-collinear magnetic transition temperature (TNC). Instead of the conventional trial-and-error approach, the composition-property descriptor is established via a data driven machine learning method named SISSO (sure independence screening and sparsifying operator). Bas… ▽ More Searching the optimal doping compositions of the Y-type hexaferrite Ba2Mg2Fe12O22 remains a long-standing challenge for enhanced non-collinear magnetic transition temperature (TNC). Instead of the conventional trial-and-error approach, the composition-property descriptor is established via a data driven machine learning method named SISSO (sure independence screening and sparsifying operator). Based on the chosen efficient and physically interpretable descriptor, a series of Y-type hexaferrite compositions are predicted to hold high TNC, among which the BaSrMg0.28Co1.72Fe10Al2O22 is then experimentally validated. Test results indicate that, under appropriate external magnetic field conditions, the TNC of this composition reaches up to reaches up to 568 K, and its magnetic transition temperature is also elevated to 735 K. This work offers a machine learning-based route to develop room temperature single phase multiferroics for device applications. △ Less

Submitted 9 July, 2024; originally announced July 2024.

Comments: accepted by Applied Physics Letters in 2024

Journal ref: Appl. Phys. Lett. 125, 032903 (2024)

Dynamical phase-field model of cavity electromagnonic systems

Authors: Shihao Zhuang, Yujie Zhu, Changchun Zhong, Liang Jiang, Xufeng Zhang, Jia-Mian Hu

Abstract: Cavity electromagnonic system, which simultaneously consists of cavities for photons, magnons (quanta of spin waves), and acoustic phonons, provides an exciting platform to achieve coherent energy transduction among different physical systems down to single quantum level. Here we report a dynamical phase-field model that allows simulating the coupled dynamics of the electromagnetic waves, magnetiz… ▽ More Cavity electromagnonic system, which simultaneously consists of cavities for photons, magnons (quanta of spin waves), and acoustic phonons, provides an exciting platform to achieve coherent energy transduction among different physical systems down to single quantum level. Here we report a dynamical phase-field model that allows simulating the coupled dynamics of the electromagnetic waves, magnetization, and strain in 3D multiphase systems. As examples of application, we computationally demonstrate the excitation of hybrid magnon-photon modes (magnon polaritons), Floquet-induced magnonic Aulter-Townes splitting, dynamical energy exchange (Rabi oscillation) and relative phase control (Ramsey interference) between the two magnon polariton modes. The simulation results are consistent with analytical calculations based on Floquet Hamiltonian theory. Simulations are also performed to design a cavity electro-magno-mechanical system that enables the triple phonon-magnon-photon resonance, where the resonant excitation of a chiral, fundamental (n=1) transverse acoustic phonon mode by magnon polaritons is demonstrated. With the capability to predict coupling strength, dissipation rates, and temporal evolution of photon/magnon/phonon mode profiles using fundamental materials parameters as the inputs, the present dynamical phase-field model represents a valuable computational tool to guide the fabrication of the cavity electromagnonic system and the design of operating conditions for applications in quantum sensing, transduction, and communication. △ Less

Submitted 24 August, 2024; v1 submitted 19 June, 2024; originally announced June 2024.

Self-correcting GKP qubit and gates in a driven-dissipative circuit

Authors: Frederik Nathan, Liam O'Brien, Kyungjoo Noh, Matthew H. Matheny, Arne L. Grimsmo, Liang Jiang, Gil Refael

Abstract: We show that a self-correcting GKP qubit can be realized with a high-impedance LC circuit coupled to a resistor and a Josephson junction via a controllable switch. When activating the switch in a particular stepwise pattern, the resonator relaxes into a subspace of GKP states that encode a protected qubit. Under continued operation, the resistor dissipatively error-corrects the qubit against bit f… ▽ More We show that a self-correcting GKP qubit can be realized with a high-impedance LC circuit coupled to a resistor and a Josephson junction via a controllable switch. When activating the switch in a particular stepwise pattern, the resonator relaxes into a subspace of GKP states that encode a protected qubit. Under continued operation, the resistor dissipatively error-corrects the qubit against bit flips and decoherence by absorbing noise-induced entropy. We show that this leads to an exponential enhancement of coherence time (T1 and T2), even in the presence of extrinsic noise, imperfect control, and device parameter variations. We show the qubit supports exponentially robust single-qubit Clifford gates, implemented via appropriate control of the switch, and readout/initialization via supercurrent measurement. The qubit's self-correcting properties allows it to operate at ~1K temperatures and resonator Q factors down to ~1000 for realistic parameters, and make it amenable to parallel control through global control signals. We discuss how the effects of quasiparticle poisoning -- potentially, though not necessarily, a limiting factor -- might be mitigated. We finally demonstrate that a related device supports a self-correcting magic T gate. △ Less

Submitted 10 April, 2025; v1 submitted 9 May, 2024; originally announced May 2024.

Comments: 16 pages + 9 figures in the main text

Construction of topological quantum magnets from atomic spins on surfaces

Authors: Hao Wang, Peng Fan, Jing Chen, Lili Jiang, Hong-Jun Gao, Jose L. Lado, Kai Yang

Abstract: Artificial quantum systems have emerged as indispensable platforms to realize exotic topological matter in a well-controlled manner. Here, we demonstrate topological quantum Heisenberg spin lattices, engineered with spin chains and two-dimensional spin arrays using spin 1/2 atoms on insulating films in a scanning tunnelling microscope (STM). We engineered with atomic precision both topological and… ▽ More Artificial quantum systems have emerged as indispensable platforms to realize exotic topological matter in a well-controlled manner. Here, we demonstrate topological quantum Heisenberg spin lattices, engineered with spin chains and two-dimensional spin arrays using spin 1/2 atoms on insulating films in a scanning tunnelling microscope (STM). We engineered with atomic precision both topological and trivial phases of the quantum spin model, realizing first- and second-order topological quantum magnets. Their many-body excitations were probed by single-atom electron spin resonance with ultrahigh energy resolution. The atomically-localized magnetic field of the STM tip allows us to directly visualize various topological bound modes including topological edge states, topological defects, and higher-order corner modes. Our results provide an important bottom-up approach to simulating exotic quantum many-body phases of interacting spins. △ Less

Submitted 3 September, 2024; v1 submitted 21 March, 2024; originally announced March 2024.

Comments: Nature Nanotechnology (2024)

Journal ref: Nature Nanotechnology 19, 1782 (2024)

Universal Spreading of Conditional Mutual Information in Noisy Random Circuits

Authors: Su-un Lee, Changhun Oh, Yat Wong, Senrui Chen, Liang Jiang

Abstract: We study the evolution of conditional mutual information in generic open quantum systems, focusing on one-dimensional random circuits with interspersed local noise. Unlike in noiseless circuits, where conditional mutual information spreads linearly while being bounded by the lightcone, we find that noisy random circuits with an error rate $p$ exhibit superlinear propagation of conditional mutual i… ▽ More We study the evolution of conditional mutual information in generic open quantum systems, focusing on one-dimensional random circuits with interspersed local noise. Unlike in noiseless circuits, where conditional mutual information spreads linearly while being bounded by the lightcone, we find that noisy random circuits with an error rate $p$ exhibit superlinear propagation of conditional mutual information, which diverges far beyond the lightcone at a critical circuit depth $t_c \propto p^{-1}$. We demonstrate that the underlying mechanism for such rapid spreading is the combined effect of local noise and a scrambling unitary, which selectively removes short-range correlations while preserving long-range correlations. To analytically capture the dynamics of conditional mutual information in noisy random circuits, we introduce a coarse-graining method, and we validate our theoretical results through numerical simulations. Furthermore, we identify a universal scaling law governing the spreading of conditional mutual information. △ Less

Submitted 3 October, 2024; v1 submitted 28 February, 2024; originally announced February 2024.

Slow-Wave Hybrid Magnonics

Authors: Jing Xu, Changchun Zhong, Shihao Zhuang, Chen Qian, Yu Jiang, Amin Pishehvar, Xu Han, Dafei Jin, Josep M. Jornet, Bo Zhen, Jiamian Hu, Liang Jiang, Xufeng Zhang

Abstract: Cavity magnonics is an emerging research area focusing on the coupling between magnons and photons. Despite its great potential for coherent information processing, it has been long restricted by the narrow interaction bandwidth. In this work, we theoretically propose and experimentally demonstrate a novel approach to achieve broadband photon-magnon coupling by adopting slow waves on engineered mi… ▽ More Cavity magnonics is an emerging research area focusing on the coupling between magnons and photons. Despite its great potential for coherent information processing, it has been long restricted by the narrow interaction bandwidth. In this work, we theoretically propose and experimentally demonstrate a novel approach to achieve broadband photon-magnon coupling by adopting slow waves on engineered microwave waveguides. To the best of our knowledge, this is the first time that slow wave is combined with hybrid magnonics. Its unique properties promise great potentials for both fundamental research and practical applications, for instance, by deepening our understanding of the light-matter interaction in the slow wave regime and providing high-efficiency spin wave transducers. The device concept can be extended to other systems such as optomagnonics and magnomechanics, opening up new directions for hybrid magnonics. △ Less

Submitted 13 February, 2024; originally announced February 2024.

Comments: 16 pages, 10 figures

Quantum-centric Supercomputing for Materials Science: A Perspective on Challenges and Future Directions

Authors: Yuri Alexeev, Maximilian Amsler, Paul Baity, Marco Antonio Barroca, Sanzio Bassini, Torey Battelle, Daan Camps, David Casanova, Young Jai Choi, Frederic T. Chong, Charles Chung, Chris Codella, Antonio D. Corcoles, James Cruise, Alberto Di Meglio, Jonathan Dubois, Ivan Duran, Thomas Eckl, Sophia Economou, Stephan Eidenbenz, Bruce Elmegreen, Clyde Fare, Ismael Faro, Cristina Sanz Fernández, Rodrigo Neumann Barros Ferreira , et al. (102 additional authors not shown)

Abstract: Computational models are an essential tool for the design, characterization, and discovery of novel materials. Hard computational tasks in materials science stretch the limits of existing high-performance supercomputing centers, consuming much of their simulation, analysis, and data resources. Quantum computing, on the other hand, is an emerging technology with the potential to accelerate many of… ▽ More Computational models are an essential tool for the design, characterization, and discovery of novel materials. Hard computational tasks in materials science stretch the limits of existing high-performance supercomputing centers, consuming much of their simulation, analysis, and data resources. Quantum computing, on the other hand, is an emerging technology with the potential to accelerate many of the computational tasks needed for materials science. In order to do that, the quantum technology must interact with conventional high-performance computing in several ways: approximate results validation, identification of hard problems, and synergies in quantum-centric supercomputing. In this paper, we provide a perspective on how quantum-centric supercomputing can help address critical computational problems in materials science, the challenges to face in order to solve representative use cases, and new suggested directions. △ Less

Submitted 19 September, 2024; v1 submitted 14 December, 2023; originally announced December 2023.

Comments: 65 pages, 15 figures; comments welcome

Journal ref: Future Generation Computer Systems, Volume 160, November 2024, Pages 666-710

Dynamical transition in controllable quantum neural networks with large depth

Authors: Bingzhi Zhang, Junyu Liu, Xiao-Chuan Wu, Liang Jiang, Quntao Zhuang

Abstract: Understanding the training dynamics of quantum neural networks is a fundamental task in quantum information science with wide impact in physics, chemistry and machine learning. In this work, we show that the late-time training dynamics of quantum neural networks with a quadratic loss function can be described by the generalized Lotka-Volterra equations, which lead to a transcritical bifurcation tr… ▽ More Understanding the training dynamics of quantum neural networks is a fundamental task in quantum information science with wide impact in physics, chemistry and machine learning. In this work, we show that the late-time training dynamics of quantum neural networks with a quadratic loss function can be described by the generalized Lotka-Volterra equations, which lead to a transcritical bifurcation transition in the dynamics. When the targeted value of loss function crosses the minimum achievable value from above to below, the dynamics evolve from a frozen-kernel dynamics to a frozen-error dynamics, showing a duality between the quantum neural tangent kernel and the total error. In both regions, the convergence towards the fixed point is exponential, while at the critical point becomes polynomial. We provide a non-perturbative analytical theory to explain the transition via a restricted Haar ensemble at late time, when the output state approaches the steady state. Via mapping the Hessian to an effective Hamiltonian, we also identify a linearly vanishing gap at the transition point. Compared with the linear loss function, we show that a quadratic loss function within the frozen-error dynamics enables a speedup in the training convergence. The theory findings are verified experimentally on IBM quantum devices. △ Less

Submitted 5 October, 2024; v1 submitted 29 November, 2023; originally announced November 2023.

Comments: 11+45 pages, comments are welcomed

Journal ref: Nat Commun 15, 9354 (2024)

Quantum-well resonances caused by partial confinement in MgO-based magnetic tunnel junctions

Authors: L. N. Jiang, B. Y. Chi, W. Z. Chen, X. F. Han

Abstract: Quantum-well resonance is achieved through partial confinement in magnetic tunnel junctions (MTJs), which provides an additional operable degree of freedom to regulate quantum-well levels. Using Al/Fe/MgO/Fe/Al and Ag/Al/Fe/MgO/Fe/Al/Ag MTJs as examples, via first-principles calculations, we demonstrate that the partial confinement of $Δ_1$ electron at Al/Fe interface and the full confinement at F… ▽ More Quantum-well resonance is achieved through partial confinement in magnetic tunnel junctions (MTJs), which provides an additional operable degree of freedom to regulate quantum-well levels. Using Al/Fe/MgO/Fe/Al and Ag/Al/Fe/MgO/Fe/Al/Ag MTJs as examples, via first-principles calculations, we demonstrate that the partial confinement of $Δ_1$ electron at Al/Fe interface and the full confinement at Fe/MgO interface combine to produce quantum-well resonances in Fe. The quantum-well levels of Fe can be periodically adjusted by two degrees of freedom: Fe and Al thickness. The oscillation period obtained from conductance $G_{\uparrow\uparrow}$ is 2.13 ML Fe (9 ML Al), close to 2.25 ML Fe (8.33 ML Al) calculated by bcc-Fe (fcc-Al) band. The combination of long and short periods enables quantum-well levels to be finely adjusted. An ultrahigh optimistic TMR effect of $3.05\times10$$^5$\% is achieved. Our results provides a new path for designing and applying quantum-well resonances in spintronics devices. △ Less

Submitted 7 April, 2024; v1 submitted 19 November, 2023; originally announced November 2023.

Signature of Topological Semimetal in Harmonic-honeycomb ReO3

Authors: Yifeng Han, Cui-Qun Chen, Hualei Sun, Shuang Zhao, Long Jiang, Yuxuan Liu, Zhongxiong Sun, Meng Wang, Hongliang Dong, Ziyou Zhang, Zhiqiang Chen, Bin Chen, Dao-Xin Yao, Man-Rong Li

Abstract: Transition-metal honeycomb compounds are capturing scientific attention due to their distinctive electronic configurations, underscored by the triangular-lattice spin-orbit coupling and competition between multiple interactions, paving the way for potential manifestations of phenomena such as Dirac semimetal, superconductivity, and quantum spin liquid states. These compounds can undergo discernibl… ▽ More Transition-metal honeycomb compounds are capturing scientific attention due to their distinctive electronic configurations, underscored by the triangular-lattice spin-orbit coupling and competition between multiple interactions, paving the way for potential manifestations of phenomena such as Dirac semimetal, superconductivity, and quantum spin liquid states. These compounds can undergo discernible pressure-induced alterations in their crystallographic and electronic paradigms, as exemplified by our high-pressure (HP) synthesis and exploration of the honeycomb polymorph of ReO3 (P6322). This HP-P6322 polymorph bears a phase transition from P6322 to P63/mmc upon cooling around Tp = 250 K, as evidenced by the evolution of temperature-dependent magnetization (M-T curves), cell dimension, and conductivity initiated by an inherent bifurcation of the oxygen position in the ab plane. Insightful analysis of its band structure positions suggests this HP-P6322 polymorph being a plausible candidate for Dirac semimetal properties. This phase transition evokes anomalies in the temperature-dependent variation of paramagnetism (non-linearity) and a crossover from semiconductor to temperature-independent metal, showing a temperature independent conductivity behavior below ~200 K. Under increasing external pressure, both the Tp and resistance of this HP-polymorph is slightly magnetic-field dependent and undergo a "V"-style evolution (decreasing and then increasing) before becoming pressure independent up to 20.2 GPa. Theoretical calculations pinpoint this anionic disorder as a probable catalyst for the decrement in the conductive efficiency and muted temperature-dependent conductivity response. △ Less

Submitted 28 December, 2023; v1 submitted 31 October, 2023; originally announced October 2023.

Journal ref: Materials Today Physics 40,101309 (2024)

V2C MXene-modified g-C3N4 for enhanced visible-light photocatalytic activity

Authors: Ruizheng Xu, Guiyu Wei, Zhemin Xie, Sijie Diao, Jianfeng Wen, Tao Tang, Li Jiang, Ming Li, Guanghui Hu

Abstract: Increasing the efficiency of charge transfer and separation efficiency of photogenerated carriers are still the main challenges in the field of semiconductor-based photocatalysts. Herein, we synthesized g-C3N4@V2C MXene photocatalyst by modifying g-C3N4 using V2C MXene. The prepared photocatalyst exhibited outstanding photocatalytic performance under visible light. The degradation efficiency of me… ▽ More Increasing the efficiency of charge transfer and separation efficiency of photogenerated carriers are still the main challenges in the field of semiconductor-based photocatalysts. Herein, we synthesized g-C3N4@V2C MXene photocatalyst by modifying g-C3N4 using V2C MXene. The prepared photocatalyst exhibited outstanding photocatalytic performance under visible light. The degradation efficiency of methyl orange by g-C3N4@V2C MXene photocatalyst was as high as 94.5%, which is 1.56 times higher than that by g-C3N4. This was attributed to the V2C MXene inhibiting the rapid recombination of photogenerated carriers and facilitating rapid transfer of photogenerated electrons (e) from g-C3N4 to MXene. Moreover, g-C3N4@V2C MXene photocatalyst showed good cycling stability. The photocatalytic performance was higher than 85% after three cycles. Experiments to capture free radicals revealed that superoxide radicals (02) are the main contributors to the photocatalytic activity. Thus, the proposed g-C3N4@V2C MXene photocatalyst is a promising visible-light catalyst. △ Less

Submitted 25 October, 2023; originally announced October 2023.

Comments: 20 pages, 9 figures

Improved iron-tolerance in recycled aluminum alloys via direct strip casting process

Authors: Lu Jiang, Ross. K. W. Marceau, Thomas Dorin

Abstract: Recycled aluminum alloys are pivotal for sustainable manufacturing, offering strength, durability, and environmental advantages. However, the presence of iron (Fe) impurities poses a major challenge, undermining their properties and recyclability. Conventional manufacturing processes result in coarse Fe-rich intermetallic compounds that limit the tolerance of Fe content and negatively influence pe… ▽ More Recycled aluminum alloys are pivotal for sustainable manufacturing, offering strength, durability, and environmental advantages. However, the presence of iron (Fe) impurities poses a major challenge, undermining their properties and recyclability. Conventional manufacturing processes result in coarse Fe-rich intermetallic compounds that limit the tolerance of Fe content and negatively influence performance of advanced aluminum alloys. To address this, rapid solidification techniques like direct strip casting have been explored. In this work, a detailed study of the strip cast microstructure was conducted by scanning electron microscopy, electron backscattered diffraction and atom probe tomography. Our results reveal that alloys produced by DSC exhibit significantly refined microstructures and are free from coarse Fe-rich intermetallics, thereby retaining the majority of Fe in solid solution. These findings indicate that strip casting significantly enhances Fe-tolerance in aluminum alloys, making it an attractive process for future aluminum recycling, with implications for sustainable high-performance applications. △ Less

Submitted 10 October, 2023; originally announced October 2023.

Efficient multimode Wigner tomography

Authors: Kevin He, Ming Yuan, Yat Wong, Srivatsan Chakram, Alireza Seif, Liang Jiang, David I. Schuster

Abstract: Advancements in quantum system lifetimes and control have enabled the creation of increasingly complex quantum states, such as those on multiple bosonic cavity modes. When characterizing these states, traditional tomography scales exponentially in both computational and experimental measurement requirement, which becomes prohibitive as the state size increases. Here, we implement a state reconstru… ▽ More Advancements in quantum system lifetimes and control have enabled the creation of increasingly complex quantum states, such as those on multiple bosonic cavity modes. When characterizing these states, traditional tomography scales exponentially in both computational and experimental measurement requirement, which becomes prohibitive as the state size increases. Here, we implement a state reconstruction method whose sampling requirement instead scales polynomially with subspace size, and thus mode number, for states that can be expressed within such a subspace. We demonstrate this improved scaling with Wigner tomography of multimode entangled W states of up to 4 modes on a 3D circuit quantum electrodynamics (cQED) system. This approach performs similarly in efficiency to existing matrix inversion methods for 2 modes, and demonstrates a noticeable improvement for 3 and 4 modes, with even greater theoretical gains at higher mode numbers. △ Less

Submitted 18 September, 2023; originally announced September 2023.

Comments: 6 pages of main text with 4 figures. 10 pages of supplementary information with 6 figures

Crystal facet orientated Altermagnets for detecting ferromagnetic and antiferromagnetic states by giant tunneling magnetoresistance effect

Authors: Boyuan Chi, Leina Jiang, Yu Zhu, Guoqiang Yu, Caihua Wan, Jia Zhang, Xiufeng Han

Abstract: Emerging altermagnetic materials with vanishing net magnetizations and unique band structures have been envisioned as an ideal electrode to design antiferromagnetic tunnel junctions. Their momentum-resolved spin splitting in band structures defines a spin-polarized Fermi surface, which allows altermagnetic materials to polarize current as a ferromagnet, when the current flows along specific direct… ▽ More Emerging altermagnetic materials with vanishing net magnetizations and unique band structures have been envisioned as an ideal electrode to design antiferromagnetic tunnel junctions. Their momentum-resolved spin splitting in band structures defines a spin-polarized Fermi surface, which allows altermagnetic materials to polarize current as a ferromagnet, when the current flows along specific directions relevant to their altermagnetism. Here, we design an Altermagnet/Insulator barrier/Ferromagnet junction, renamed as altermagnetic tunnel junction (ATMTJ), using RuO$_2$/TiO$_2$/CrO$_2$ as a prototype. Through first-principles calculations, we investigate the tunneling properties of the ATMTJ along the [001] and [110] directions, which shows that the tunneling magnetoresistance (TMR) is almost zero when the current flows along the [001] direction, while it can reach as high as 6100\% with current flows along the [110] direction. The spin-resolved conduction channels of the altermagnetic RuO$_2$ electrode are found responsible for this momentum-dependent (or transport-direction-dependent) TMR effect. Furthermore, this ATMTJ can also be used to readout the Néel vector of the altermagnetic electrode RuO$_2$. Our work promotes the understanding toward the altermagnetic materials and provides an alternative way to design magnetic tunnel junctions with ultrahigh TMR ratios and robustness of the altermagnetic electrode against external disturbance, which broadens the application avenue for antiferromagnetic spintronic devices. △ Less

Submitted 20 November, 2023; v1 submitted 18 September, 2023; originally announced September 2023.

Evidence of Kitaev interaction in the monolayer 1T-CrTe$_2$

Authors: Can Huang, Bingjie Liu, LingZi Jiang, Yanfei Pan, Jiyu Fan, Daning Shi, Chunlan Ma, Qiang Luo, Yan Zhu

Abstract: The two-dimensional 1T-CrTe$_2$ has been an attractive room-temperature van der Waals magnet which has a potential application in spintronic devices. Although it was recognized as a ferromagnetism in the past, the monolayer 1T-CrTe$_2$ was recently found to exhibit zigzag antiferromagnetism with the easy axis oriented at $70^\circ$ to the perpendicular direction of the plane. Therefore, the origin… ▽ More The two-dimensional 1T-CrTe$_2$ has been an attractive room-temperature van der Waals magnet which has a potential application in spintronic devices. Although it was recognized as a ferromagnetism in the past, the monolayer 1T-CrTe$_2$ was recently found to exhibit zigzag antiferromagnetism with the easy axis oriented at $70^\circ$ to the perpendicular direction of the plane. Therefore, the origin of the intricate anisotropic magnetic behavior therein is well worthy of thorough exploration. Here, by applying density functional theory with spin spiral method, we demonstrate that the Kitaev interaction, together with the single-ion anisotropy and other off-diagonal exchanges, is amenable to explain the magnetic orientation in the metallic 1T-CrTe$_2$. Moreover, the Ruderman-Kittle-Kasuya-Yosida interaction can also be extracted from the dispersion calculations, which explains the metallic behavior of 1T-CrTe$_2$. Our results demonstrate that 1T-CrTe$_2$ is potentially a rare metallic Kitaev material. △ Less

Submitted 27 September, 2023; v1 submitted 23 May, 2023; originally announced May 2023.

Journal ref: Phys. Rev. B. 108, 094433 (2023)

Magnetic field stabilized Wigner crystal states in a graphene moiré superlattice

Authors: Guorui Chen, Ya-Hui Zhang, Aaron Sharpe, Zuocheng Zhang, Shaoxin Wang, Lili Jiang, Bosai Lyu, Hongyuan Li, Kenji Watanabe, Takashi Taniguchi, Zhiwen Shi, David Goldhaber-Gordon, Yuanbo Zhang, Feng Wang

Abstract: Wigner crystals are predicted as the crystallization of the dilute electron gas moving in a uniform background when the electron-electron Coulomb energy dominates the kinetic energy. The Wigner crystal has previously been observed in the ultraclean two-dimensional electron gas (2DEG) present on the surface of liquid helium and in semiconductor quantum wells at high magnetic field. More recently, W… ▽ More Wigner crystals are predicted as the crystallization of the dilute electron gas moving in a uniform background when the electron-electron Coulomb energy dominates the kinetic energy. The Wigner crystal has previously been observed in the ultraclean two-dimensional electron gas (2DEG) present on the surface of liquid helium and in semiconductor quantum wells at high magnetic field. More recently, Wigner crystals have also been reported in WS2/WSe2 moiré heterostructures. ABC-stacked trilayer graphene on boron nitride (ABC-TLG/hBN) moiré superlattices provide a unique tunable platform to explore Wigner crystal states where the electron correlation can be controlled by electric and magnetic field. Here we report the observation of magnetic field stabilized Wigner crystal states in a ABC-TLG/hBN moiré superlattice. We show that correlated insulating states emerge at multiple fractional and integer fillings corresponding to v = 1/3, 2/3, 1, 4/3, 5/3 and 2 electrons per moiré lattice site under a magnetic field. These correlated insulating states can be attributed to generalized Mott states for the integer fillings (v = 1, 2) and generalized Wigner crystal states for the fractional fillings (v = 1/3, 2/3, 4/3, 5/3). The generalized Wigner crystal states are stabilized by a vertical magnetic field, and they are strongest at one magnetic flux quantum per three moiré superlattices. The correlated insulating states at v = 2 persists up to 30 Tesla, which can be described by a Mott-Hofstadter transition at high magnetic field. The tunable Mott and Wigner crystal states in the ABC-TLG/hBN highlight the opportunities to discover new correlated quantum phases due to the interplay between the magnetic field and moiré flatbands. △ Less

Submitted 15 May, 2023; originally announced May 2023.

Comments: 19 pages, 6 figures

Magnetic field-induced weak-to-strong-link transformation in patterned superconducting films

Authors: D. A. D. Chaves, M. I. Valerio-Cuadros, L. Jiang, E. A. Abbey, F. Colauto, A. A. M. Oliveira, A. M. H. Andrade, L. B. L. G. Pinheiro, T. H. Johansen, C. Xue, Y. -H. Zhou, A. V. Silhanek, W. A. Ortiz, M. Motta

Abstract: Ubiquitous in most superconducting materials and a common result of nanofabrication processes, weak-links are known for their limiting effects on the transport of electric currents. Still, they are at the root of key features of superconducting technology. By performing quantitative magneto-optical imaging experiments and thermomagnetic model simulations, we correlate the existence of local maxima… ▽ More Ubiquitous in most superconducting materials and a common result of nanofabrication processes, weak-links are known for their limiting effects on the transport of electric currents. Still, they are at the root of key features of superconducting technology. By performing quantitative magneto-optical imaging experiments and thermomagnetic model simulations, we correlate the existence of local maxima in the magnetization loops of FIB-patterned Nb films to a magnetic field-induced weak-to-strong-link transformation increasing their critical current. This phenomenon arises from the nanoscale interaction between quantized magnetic flux lines and FIB-induced modifications of the device microstructure. Under an ac drive field, this leads to a rectified vortex motion along the weak-link. The reported tunable effect can be exploited in the development of new superconducting electronic devices, such as flux pumps and valves, to attenuate or amplify the supercurrent through a circuit element, and as a strategy to enhance the critical current in weak-link-bearing devices. △ Less

Submitted 9 October, 2023; v1 submitted 7 May, 2023; originally announced May 2023.

Comments: 11 pages and 8 figures

Variant Plateau Law in Atomically Thin Transition Metal Dichalcogenide Dome Networks

Authors: Boqing Liu, Tanju Yildirim, Tieyu Lv, Elena Blundo, Li Wang, Lixue Jiang, Hongshuai Zou, Lijun Zhang, Huijun Zhao, Zongyou Yin, Fangbao Tian, Antonio Polimeni, Yuerui Lu

Abstract: Since its fundamental inception from soap bubbles, Plateau law has sparked extensive research in equilibrated states. However, most studies primarily relied on liquids, foams or cellular structures, whereas its applicability has yet to be explored in nano-scale solid films. Here, we observed a variant Plateau law in networks of atomically thin domes made of solid two-dimensional (2D) transition me… ▽ More Since its fundamental inception from soap bubbles, Plateau law has sparked extensive research in equilibrated states. However, most studies primarily relied on liquids, foams or cellular structures, whereas its applicability has yet to be explored in nano-scale solid films. Here, we observed a variant Plateau law in networks of atomically thin domes made of solid two-dimensional (2D) transition metal dichalcogenides (TMDs). Discrete layer-dependent van der Waals (vdWs) interaction energies were experimentally and theoretically obtained for domes protruding in different TMD layers. Significant surface tension differences from layer-dependent vdWs interaction energies manifest in a variant of this fundamental law. Meanwhile, the remarkable mechanical properties, gas impermeability and interlayer vdWs interaction energy of TMD films enable domes and the networks to sustain high gas pressure and exist in a fundamentally variant nature for several years. Our findings pave the way towards exploring variant discretised states with applications in opto-electro-mechanical devices. △ Less

Submitted 13 February, 2023; v1 submitted 9 February, 2023; originally announced February 2023.

Unconventional polarization switching mechanism in (Hf, Zr)O2 ferroelectrics

Authors: Yao Wu, Yuke Zhang, Jie Jiang, Limei Jiang, Minghua Tang, Yichun Zhou, Min Liao, Qiong Yang, Evgeny Y. Tsymbal

Abstract: HfO$_{2}$-based ferroelectric thin films are promising for their application in ferroelectric devices. Predicting the ultimate magnitude of polarization and understanding its switching mechanism are critical to realize the optimal performance of these devices. Here, a generalized solid-state variable cell nudged elastic band (VCNEB) method is employed to predict the switching pathway associated wi… ▽ More HfO$_{2}$-based ferroelectric thin films are promising for their application in ferroelectric devices. Predicting the ultimate magnitude of polarization and understanding its switching mechanism are critical to realize the optimal performance of these devices. Here, a generalized solid-state variable cell nudged elastic band (VCNEB) method is employed to predict the switching pathway associated with domain-wall motion in (Hf, Zr)O$_{2}$ ferroelectrics. It is found that the polarization reversal pathway, where three-fold coordinated O atoms pass across the nominal unit-cell boundaries defined by the Hf/Zr atomic planes, is energetically more favorable than the conventional pathway where the O atoms do not pass through these planes. This finding implies that the polarization orientation in the orthorhombic Pca2$_{1}$ phase of HfO$_{2}$ nd its derivatives is opposite to that normally assumed, predicts the spontaneous polarization magnitude of about 70 $μ$C/cm$^{2}$ that is nearly 50% larger than the commonly accepted value, signifies a positive intrinsic longitudinal piezoelectric coefficient, and suggests growth of ferroelectric domains, in response to an applied electric field, structurally reversed to those usually anticipated. These results provide important insights into the understanding of ferroelectricity in HfO$_{2}$-based ferroelectrics. △ Less

Submitted 3 April, 2023; v1 submitted 15 January, 2023; originally announced January 2023.

Comments: 34 pages, 28 figures

Unconventionally Fast Transport through Sliding Dynamics of Rodlike Particles in Macromolecular Networks

Authors: Xuanyu Zhang, Xiaobin Dai, Md Ahsan Habib, Ziyang Xu, Lijuan Gao, Wenlong Chen, Wenjie Wei, Zhongqiu Tang, Xianyu Qi, Xiangjun Gong, Lingxiang Jiang, Li-Tang Yan

Abstract: Transport of rodlike particles in confinement environments of macromolecular networks plays crucial roles in many important biological processes and technological applications. The relevant understanding has been limited to thin rods with diameter much smaller than network mesh size, although the opposite case, of which the dynamical behaviors and underlying physical mechanisms remain unclear, is… ▽ More Transport of rodlike particles in confinement environments of macromolecular networks plays crucial roles in many important biological processes and technological applications. The relevant understanding has been limited to thin rods with diameter much smaller than network mesh size, although the opposite case, of which the dynamical behaviors and underlying physical mechanisms remain unclear, is ubiquitous. Here, we solve this issue by combining experiments, simulations and theory. We find a nonmonotonic dependence of translational diffusion on rod length, characterized by length commensuration-governed unconventionally fast dynamics which is in striking contrast to the monotonic dependence for thin rods. Our results clarify that such a fast diffusion of thick rods with length of integral multiple of mesh size follows sliding dynamics and demonstrate it to be "anomalous yet Brownian". Moreover, good agreement between theoretical analysis and simulations corroborates that the sliding dynamics is an intermediate regime between hopping and Brownian dynamics, and provides a mechanistic interpretation based on the rod-length dependent entropic free energy barrier. The findings yield a principle, that is, length commensuration, for optimal design of rodlike particles with highly efficient transport in confined environments of macromolecular networks, and might enrich the physics of the diffusion dynamics in heterogeneous media. △ Less

Submitted 19 November, 2023; v1 submitted 26 December, 2022; originally announced December 2022.

Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films

Authors: L. B. L. G. Pinheiro, L. Jiang, E. A. Abbey, Davi A. D. Chaves, A. J. Chiquito, T. H. Johansen, J. Van de Vondel, C. Xue, Y. -H. Zhou, A. V. Silhanek, W. A. Ortiz, M. Motta

Abstract: Thickness uniformity is regarded as an important parameter in designing thin film devices. However, some applications based on films with non-uniform thickness have recently emerged, such as gas sensors and optimized materials based on the gradual change of film composition. This work deals with superconducting Pb thin films with a thickness gradient prepared with the aid of a diffuse stencil mask… ▽ More Thickness uniformity is regarded as an important parameter in designing thin film devices. However, some applications based on films with non-uniform thickness have recently emerged, such as gas sensors and optimized materials based on the gradual change of film composition. This work deals with superconducting Pb thin films with a thickness gradient prepared with the aid of a diffuse stencil mask. Atomic Force Microscopy and Energy-Dispersive X-ray Spectroscopy show variations ranging from 90~nm to 154~nm. Quantitative magneto-optical images reveal interesting features during both the abrupt and the smooth penetration regimes of magnetic flux, as well as the thickness-dependent critical current density ($J_c$). In addition, we observe a gradual superconducting transition as the upper critical field is progressively reached for certain thicknesses. Furthermore, the hysteresis observed for triggering flux avalanches when increasing and decreasing magnetic fields is also accounted for by the $J_c$ profile evolution along the thickness gradient. Numerical simulations based on the Thermomagnetic Model are in fair agreement with the experimental data. These findings demonstrate that wedge-shaped films are a viable approach to investigate, in a continuous fashion, thickness-dependent properties of a superconducting materials. △ Less

Submitted 18 October, 2022; originally announced October 2022.

Failure behaviors and processing maps with failure domains for hot compression of a powder metallurgy Ni-based superalloy

Authors: Zonglin Chi, Shuai Ren, Jingbo Qiao, Jinglong Qu, Chengbin Yang, Zhuanye Xie, Wei Chen, Hua Zhang, Liang Jiang, Shuying Chen, Fanchao Meng

Abstract: Processing maps are key to guiding the thermo-mechanical processing (TMP) of superalloys. However, traditional processing maps are incapable of delimiting failure, which is an essential factor to be concerned about during the TMP of superalloys. Employing isothermal hot compression experiments and finite element analysis (FEA), the present study examined the failure behaviors of a powder metallurg… ▽ More Processing maps are key to guiding the thermo-mechanical processing (TMP) of superalloys. However, traditional processing maps are incapable of delimiting failure, which is an essential factor to be concerned about during the TMP of superalloys. Employing isothermal hot compression experiments and finite element analysis (FEA), the present study examined the failure behaviors of a powder metallurgy (P/M) Ni-based superalloy and constructed processing maps with failure domains based on the predicted failure threshold. The micromechanical Gurson-Tvergaard-Needleman (GTN) damage model was employed in the FEA to model the cavity-driven intergranular fracture of the superalloy. Deformation temperature and strain rate were considered in the range of 1050 ~ 1150 C and 0.001 ~ 1 s-1, respectively. The FEA results reveal that the maximum tensile stress locates at the outer budging surfaces of the samples, which causes failure initiation and subsequent propagation into longitudinal cracks, being consistent with the experiments. It is further demonstrated that the failure is strain-controlled and the critical failure strain remains nearly insensitive to the range of strain rates considered while increasing with the increase of temperature in a third-order polynomial. Finally, an optimized processing window for hot deformation of the superalloy is formulated to warrant good hot workability while avoiding flow instability and failure. The present study offers direct insights into the failure behaviors of P/M Ni-based superalloys and details a modeling strategy to delineate optimized parametric spaces for the TMP of superalloys. △ Less

Submitted 22 August, 2022; originally announced August 2022.

Crystal and electronic structure of a quasi-two-dimensional semiconductor Mg$_3$Si$_2$Te$_6$

Authors: Chaoxin Huang, Benyuan Cheng, Yunwei Zhang, Long Jiang, Lisi Li, Mengwu Huo, Hui Liu, Xing Huang, Feixiang Liang, Lan Chen, Hualei Sun, Meng Wang

Abstract: We report the synthesis and characterization of a Si-based ternary semiconductor Mg$_3$Si$_2$Te$_6$, which exhibits a quasi-two-dimensional structure, where the trigonal Mg$_2$Si$_2$Te$_6$ layers are separated by Mg ions. Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure. The experimentally determined direc… ▽ More We report the synthesis and characterization of a Si-based ternary semiconductor Mg$_3$Si$_2$Te$_6$, which exhibits a quasi-two-dimensional structure, where the trigonal Mg$_2$Si$_2$Te$_6$ layers are separated by Mg ions. Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure. The experimentally determined direct band gap is 1.39 eV, consistent with the value of the density function theory calculations. Our results reveal that Mg$_3$Si$_2$Te$_6$ is a direct gap semiconductor with a relatively narrow gap, which is a potential candidate for infrared optoelectronic devices. △ Less

Submitted 12 July, 2022; originally announced July 2022.

Comments: 5 pages, 5 figures

Report number: https://iopscience.iop.org/article/10.1088/1674-1056/aca393

Journal ref: Chinese Physics B, 2022

Gravity-induced accelerating expansion of excited-state Bose-Einstein condensate

Authors: Lijia Jiang, Jun-Hui Zheng

Abstract: The Bose-Einstein condensate (BEC) of excited states, provides a different platform to explore the interplay between gravity and quantum physics. In this Letter, we study the response of excited-state BECs to an external gravitational field and their dynamics under gravity when space is expanding. We reveal the anomalous response of the center-of-mass of the BEC to the gravitational field and the… ▽ More The Bose-Einstein condensate (BEC) of excited states, provides a different platform to explore the interplay between gravity and quantum physics. In this Letter, we study the response of excited-state BECs to an external gravitational field and their dynamics under gravity when space is expanding. We reveal the anomalous response of the center-of-mass of the BEC to the gravitational field and the exotic gravity-induced accelerating expansion phenomena. We demonstrate that these effects result from the interplay among gravity, space and quantum effects. We also propose related experiments to observe these anomalies. △ Less

Submitted 21 May, 2023; v1 submitted 30 June, 2022; originally announced June 2022.

Comments: 5 pages, 3 figures

Electron spin coherence on a solid neon surface

Authors: Qianfan Chen, Ivar Martin, Liang Jiang, Dafei Jin

Abstract: A single electron floating on the surface of a condensed noble-gas liquid or solid can act as a spin qubit with ultralong coherence time, thanks to the extraordinary purity of such systems. Previous studies suggest that the electron spin coherence time on a superfluid helium (He) surface can exceed 100 s. In this paper, we present theoretical studies of the electron spin coherence on a solid neon… ▽ More A single electron floating on the surface of a condensed noble-gas liquid or solid can act as a spin qubit with ultralong coherence time, thanks to the extraordinary purity of such systems. Previous studies suggest that the electron spin coherence time on a superfluid helium (He) surface can exceed 100 s. In this paper, we present theoretical studies of the electron spin coherence on a solid neon (Ne) surface, motivated by our recent experimental realization of single-electron charge qubit on solid Ne. The major spin decoherence mechanisms investigated include the fluctuating Ne diamagnetic susceptibility due to thermal phonons, the fluctuating thermal current in normal metal electrodes, and the quasi-statically fluctuating nuclear spins of the $^{21}$Ne ensemble. We find that at a typical experimental temperature about 10 mK in a fully superconducting device, the electron spin decoherence is dominated by the third mechanism via electron-nuclear spin-spin interaction. For natural Ne with 2700 ppm abundance of $^{21}$Ne, the estimated inhomogeneous dephasing time $T_{2}^{*}$ is around 0.16 ms, already better than most semiconductor quantum-dot spin qubits. For commercially available, isotopically purified Ne with 1 ppm of $^{21}$Ne, $T_{2}^{*}$ can be $0.43$ s. Under the application of Hahn echoes, the coherence time $T_{2}$ can be improved to $30$ ms for natural Ne and $81$ s for purified Ne. Therefore, the single-electron spin qubits on solid Ne can serve as promising new spin qubits. △ Less

Submitted 3 August, 2022; v1 submitted 1 May, 2022; originally announced May 2022.

Spectroscopy Signatures of Electron Correlations in a Trilayer Graphene/hBN Moiré Superlattice

Authors: Jixiang Yang, Guorui Chen, Tianyi Han, Qihang Zhang, Ya-Hui Zhang, Lili Jiang, Bosai Lyu, Hongyuan Li, Kenji Watanabe, Takashi Taniguchi, Zhiwen Shi, Todadri Senthil, Yuanbo Zhang, Feng Wang, Long Ju

Abstract: ABC-stacked trilayer graphene/hBN moiré superlattice (TLG/hBN) has emerged as a playground for correlated electron physics. We report spectroscopy measurements of dual-gated TLG/hBN using Fourier transformed infrared photocurrent spectroscopy. We observed a strong optical transition between moiré mini-bands that narrows continuously as a bandgap is opened by gating, indicating a reduction of the s… ▽ More ABC-stacked trilayer graphene/hBN moiré superlattice (TLG/hBN) has emerged as a playground for correlated electron physics. We report spectroscopy measurements of dual-gated TLG/hBN using Fourier transformed infrared photocurrent spectroscopy. We observed a strong optical transition between moiré mini-bands that narrows continuously as a bandgap is opened by gating, indicating a reduction of the single particle bandwidth. At half-filling of the valence flat band, a broad absorption peak emerges at ~18 meV, indicating direct optical excitation across an emerging Mott gap. Similar photocurrent spectra are observed in two other correlated insulating states at quarter- and half-filling of the first conduction band. Our findings provide key parameters of the Hubbard model for the understanding of electron correlation in TLG/hBN. △ Less

Submitted 2 March, 2022; v1 submitted 24 February, 2022; originally announced February 2022.

Comments: 17 pages; 4 figures; supplementary materials: 13 pages; Science (2022, in press)

Universal and Efficient p-Doping of Organic Semiconductors by Electrophilic Attack of Cations

Authors: Jing Guo, Ying Liu, Ping-An Chen, Xinhao Wang, Yanpei Wang, Jing Guo, Xincan Qiu, Zebing Zeng, Lang Jiang, Yuanping Yi, Shun Watanabe, Lei Liao, Yugang Bai, Thuc-Quyen Nguyen, Yuanyuan Hu

Abstract: Doping is of great importance to tailor the electrical properties of semiconductors. However, the present doping methodologies for organic semiconductors (OSCs) are either inefficient or can only apply to a small number of OSCs, seriously limiting their general application. Herein, we reveal a novel p-doping mechanism by investigating the interactions between the dopant trityl cation and poly(3-he… ▽ More Doping is of great importance to tailor the electrical properties of semiconductors. However, the present doping methodologies for organic semiconductors (OSCs) are either inefficient or can only apply to a small number of OSCs, seriously limiting their general application. Herein, we reveal a novel p-doping mechanism by investigating the interactions between the dopant trityl cation and poly(3-hexylthiophene) (P3HT). It is found that electrophilic attack of the trityl cations on thiophenes results in the formation of alkylated ions that induce electron transfer from neighboring P3HT chains, resulting in p-doping. This unique p-doping mechanism can be employed to dope various OSCs including those with high ionization energy (IE=5.8 eV). Moreover, this doping mechanism endows trityl cation with strong doping ability, leading to polaron yielding efficiency of 100 % and doping efficiency of over 80 % in P3HT. The discovery and elucidation of this novel doping mechanism not only points out that strong electrophiles are a class of efficient p-dopants for OSCs, but also provides new opportunities towards highly efficient doping of OSCs. △ Less

Submitted 14 February, 2022; originally announced February 2022.

Accumulation and alignment of elongated gyrotactic swimmers in turbulence

Authors: Zehua Liu, Linfeng Jiang, Chao Sun

Abstract: We study the dynamics of gyrotactic swimmers in turbulence, whose orientation is governed by gravitational torque and local fluid velocity gradient. The gyrotaxis strength is measured by the ratio of the Kolmogorov time scale to the reorientation time scale due to gravity, and a large value of this ratio means the gyrotaxis is strong. By means of direct numerical simulations, we investigate the ef… ▽ More We study the dynamics of gyrotactic swimmers in turbulence, whose orientation is governed by gravitational torque and local fluid velocity gradient. The gyrotaxis strength is measured by the ratio of the Kolmogorov time scale to the reorientation time scale due to gravity, and a large value of this ratio means the gyrotaxis is strong. By means of direct numerical simulations, we investigate the effects of swimming velocity and gyrotactic stability on spatial accumulation and alignment. Three-dimensional Vorono{\"ı} analysis is used to study the spatial distribution and time evolution of the particle concentration. We study spatial distribution by examing the overall preferential sampling and where clusters and voids (subsets of particles that have small and large Vorono{\"ı} volumes respectively) form. Compared with the ensemble particles, the preferential sampling of clusters and voids is found to be more pronounced. The clustering of fast swimmers lasts much longer than slower swimmers when the gyrotaxis is strong and intermediate, but an opposite trend emerges when the gyrotaxis is weak. In addition, we study the preferential alignment with the Lagrangian stretching direction, with which passive slender rods have been known to align. We show that the Lagrangian alignment is reduced by the swimming velocity when the gyrotaxis is weak, while the Lagrangian alignment is enhanced for the regime in which gyrotaxis is strong. △ Less

Submitted 9 February, 2022; originally announced February 2022.

Dynamics of finite-size spheroids in turbulent flow: the roles of flow structures and particle boundary layers

Authors: Linfeng Jiang, Cheng Wang, Shuang Liu, Chao Sun, Enrico Calzavarini

Abstract: We study the translational and rotational dynamics of neutrally-buoyant finite-size spheroids in hydrodynamic turbulence by means of fully resolved numerical simulations. We examine axisymmetric shapes, from oblate to prolate, and the particle volume dependences. We show that the accelerations and rotations experienced by non-spherical inertial-scale particles result from volume filtered fluid for… ▽ More We study the translational and rotational dynamics of neutrally-buoyant finite-size spheroids in hydrodynamic turbulence by means of fully resolved numerical simulations. We examine axisymmetric shapes, from oblate to prolate, and the particle volume dependences. We show that the accelerations and rotations experienced by non-spherical inertial-scale particles result from volume filtered fluid forces and torques, similar to spherical particles. However, the particle orientations carry signatures of preferential alignments with the surrounding flow structures, which is reflected in distinct axial and lateral fluctuations for accelerations and rotation rates. The randomization of orientations does not occur even for particles with volume equivalent diameter size in the inertial range, here up to 60 $η$ at $Re_λ=120$. Additionally, we demonstrate that the role of fluid boundary layers around the particles cannot be neglected to reach a quantitative understanding of particle statistical dynamics, as they affect the intensities of angular velocities, and the relative importance of tumbling with respect to spinning rotations. This study brings to the fore the importance of inertial-scale flow structures in homogeneous and isotropic turbulence and their impacts on the transport of neutrally-buoyant bodies with size in the inertial range. △ Less

Submitted 8 February, 2022; originally announced February 2022.

Comments: 21 pages, 11 figures

Journal ref: J. Fluid Mech. 939, A22 (2022)

Clifford-deformed Surface Codes

Authors: Arpit Dua, Aleksander Kubica, Liang Jiang, Steven T. Flammia, Michael J. Gullans

Abstract: Various realizations of Kitaev's surface code perform surprisingly well for biased Pauli noise. Attracted by these potential gains, we study the performance of Clifford-deformed surface codes (CDSCs) obtained from the surface code by applying single-qubit Clifford operators. We first analyze CDSCs on the $3\times 3$ square lattice and find that, depending on the noise bias, their logical error rat… ▽ More Various realizations of Kitaev's surface code perform surprisingly well for biased Pauli noise. Attracted by these potential gains, we study the performance of Clifford-deformed surface codes (CDSCs) obtained from the surface code by applying single-qubit Clifford operators. We first analyze CDSCs on the $3\times 3$ square lattice and find that, depending on the noise bias, their logical error rates can differ by orders of magnitude. To explain the observed behavior, we introduce the effective distance $d'$, which reduces to the standard distance for unbiased noise. To study CDSC performance in the thermodynamic limit, we focus on random CDSCs. Using the statistical mechanical mapping for quantum codes, we uncover a phase diagram that describes random CDSC families with $50\%$ threshold at infinite bias. In the high-threshold region, we further demonstrate that typical code realizations outperform the thresholds and subthreshold logical error rates, at finite bias, of the best-known translationally invariant codes. We demonstrate the practical relevance of these random CDSC families by constructing a translation-invariant CDSC belonging to a high-performance random CDSC family. We also show that our translation-invariant CDSC outperforms well-known translation-invariant CDSCs such as the XZZX and XY codes. △ Less

Submitted 27 February, 2024; v1 submitted 19 January, 2022; originally announced January 2022.

Comments: 6+10 pages, 14 figures, v2 changes: added a section on a translation-invariant code belonging to a high-performance random CDSC family to demonstrate the practical relevance of the random CDSCs. The code used for the simulations in the paper is available at https://github.com/dua-arpit/qecsim. See also https://errorcorrectionzoo.org/c/clifford-deformed_surface, v3 changes: PRX Quantum version

Journal ref: PRX Quantum 5, 010347 (2024)

Strain-engineered high-temperature ferromagnetic Oxygen-substituted NaMnF3 from first principles

Authors: Wenning Ren, Kuijuan Jin, Erjia Guo, Chen Ge, Can Wang, Xiulai Xu, Hongbao Yao, Litong Jiang, Guozhen Yang

Abstract: Using first-principles calculations, we investigated the magnetic, electronic, and structural properties of oxygen-substituted NaMnF3 (NaMnF1.5O1.5) with in-plane biaxial strain. For simplicity, a structure containing an oxygen octahedron is used to explore the underlying physical mechanism. We found that the oxygen octahedron induces a transition from an insulating antiferromagnet to a high-tempe… ▽ More Using first-principles calculations, we investigated the magnetic, electronic, and structural properties of oxygen-substituted NaMnF3 (NaMnF1.5O1.5) with in-plane biaxial strain. For simplicity, a structure containing an oxygen octahedron is used to explore the underlying physical mechanism. We found that the oxygen octahedron induces a transition from an insulating antiferromagnet to a high-temperature half-metallic ferromagnet. More importantly, the Curie temperature can be significantly enhanced and even might reach room temperature by applying tensile strain. The changing trends of exchange coupling constants with the increasing biaxial tensile strain can be attributed to the cooperative effects of Jahn-Teller distortion and rotation distortion. It is expected that these findings can enrich the versatility of NaMnF3 and make it a promising candidate for spintronic applications. △ Less

Submitted 17 January, 2022; originally announced January 2022.

Comments: 24 pages 6 figures

DASP: Defect and Dopant ab-initio Simulation Package

Authors: Menglin Huang, Zhengneng Zheng, Zhenxing Dai, Xinjing Guo, Shanshan Wang, Lilai Jiang, Jinchen Wei, Shiyou Chen

Abstract: In order to perform automated calculations of defect and dopant properties in semiconductors and insulators, we developed a software package, Defect and Dopant ab-initio Simulation Package (DASP), which is composed of four modules for calculating: (i) elemental chemical potentials, (ii) defect (dopant) formation energies and transition energy levels, (iii) defect and carrier densities and (iv) car… ▽ More In order to perform automated calculations of defect and dopant properties in semiconductors and insulators, we developed a software package, Defect and Dopant ab-initio Simulation Package (DASP), which is composed of four modules for calculating: (i) elemental chemical potentials, (ii) defect (dopant) formation energies and transition energy levels, (iii) defect and carrier densities and (iv) carrier dynamics properties of high-density defects. DASP uses the materials genome database for quick determination of competing secondary phases and calculation of the energy above convex hull when calculating the elemental chemical potential that stabilizes compound semiconductors, so it can perform high-throughput prediction of thermodynamic stability of multinary compounds. DASP calls the ab-initio softwares to perform the total energy, structural relaxation and electronic structure calculations of the defect supercells with different structure configurations and charge states, based on which the defect formation energies and transition energy levels are calculated and the corrections for electrostatic potential alignment and image charge interaction can be included. Then DASP can calculate the equilibrium densities of defects and electron and hole carriers as well as the Fermi level in semiconductors under different chemical potential conditions and different growth/working temperature. For high-density defects, DASP can calculate the carrier dynamics properties such as the photoluminescence (PL) spectrum, defect-related radiative and non-radiative carrier capture cross sections, and recombination lifetime of non-equilibrium carriers. △ Less

Submitted 6 January, 2022; originally announced January 2022.

Comments: 33 pages, 11 figures

Journal ref: Journal of Semiconductors 43, 042101 (2022)