Showing 1–50 of 121 results for author: Shi, T

Testing the Reptation Picture: Topological Constraint from Monomer Dynamics

Authors: Xiaofei Tian, Qinhang Liu, Zhi-Chao Yan, Liang Gao, Tongfei Shi, Jizhong Chen

Abstract: The reptation model postulates that entangled polymers slide within a fractal tube. Here we employ a model-independent relation between the zero-displacement probability and the mean-square displacement that applies to time-dependent fractal structures, enabling direct measurement of the fractal dimension $d_\mathrm{f}$ of the geometry experienced by monomer motion. For two-dimensional obstacle ar… ▽ More The reptation model postulates that entangled polymers slide within a fractal tube. Here we employ a model-independent relation between the zero-displacement probability and the mean-square displacement that applies to time-dependent fractal structures, enabling direct measurement of the fractal dimension $d_\mathrm{f}$ of the geometry experienced by monomer motion. For two-dimensional obstacle arrays and in the slip-link model, $d_\mathrm{f}$ agrees with the reptation prediction $d_\mathrm{f}=1/ν$ (where $ν$ is the Flory exponent). In polymer melts, however, we find $d_\mathrm{f} \approx 2.6$ --- a value close to the fractal dimension of percolation clusters, not the reptation value $d_\mathrm{f}=2$. This contrasts sharply with the reptation picture, in which a Rouse chain slides in a fractal structure with $d_\mathrm{f}=2$, spectral dimension $d_\mathrm{s}=1$, and walk dimension $d_\mathrm{w}=4$; our results point instead to a percolation-like scenario, characterized by $d_\mathrm{f}\approx 2.6$, $d_\mathrm{s}\approx 1.3$, and $d_\mathrm{w}\approx 4$ --- revealing a dynamically emergent, finite-size fractal geometry distinct from the static tube. △ Less

Submitted 14 August, 2026; originally announced August 2026.

Soft point-contact Andreev reflection spectroscopy in a palm-type cubic anvil-pressure cell

Authors: Qingxin Dong, Fengrui Shi, Yan Zhang, Tong Shi, Yi Liu, Shaoheng Ruan, Zhongjin Wu, Jianping Sun, Zhaoming Tian, Yoshiya Uwatoko, Guanghan Cao, Xin Lu, Bosen Wang, Jin-Guang Cheng

Abstract: We have implemented soft point-contact Andreev reflection spectroscopy (PCARS) in a palm-type cubic anvil pressure cell by combining a substrate anchoring strategy with an external wire-splitting technique. This design enables the stable formation of multiple point contact junctions under hydrostatic pressures up to 15 GPa. Benchmark measurements on the elemental superconductor Nb demonstrate high… ▽ More We have implemented soft point-contact Andreev reflection spectroscopy (PCARS) in a palm-type cubic anvil pressure cell by combining a substrate anchoring strategy with an external wire-splitting technique. This design enables the stable formation of multiple point contact junctions under hydrostatic pressures up to 15 GPa. Benchmark measurements on the elemental superconductor Nb demonstrate high reproducibility and yield a zero-temperature superconducting gap with a gap ratio of 3.3. We further apply this technique to the Kagome metal superconductor CsCr3Sb5 and the bilayer nickelate superconductor La2PrNi2O7. Pronounced zero-bias conductance peaks are observed, and their evolution with temperature, magnetic field and applied pressure is investigated, together with the superconducting gap magnitude and possible pairing symmetries. These measurements provide spectroscopic evidence consistent with unconventional superconductivity in these materials. Our work establishes a robust experimental platform that bridges macroscopic electrical transport and microscopic spectroscopic probes, opening a new avenue for investigating pairing symmetry in a wide range of pressure-induced unconventional superconductors. △ Less

Submitted 12 July, 2026; originally announced July 2026.

Comments: 16 pages, 4 figures

Scalable Simulation of Strongly Correlated Electron-Phonon Systems via Non-Gaussian Matrix Product States

Authors: Siyuan Jiang, Tao Shi

Abstract: We investigate strongly correlated electron-phonon (e-ph) systems via a non-Gaussian matrix product state method. By combining non-Gaussian states with matrix product states, our method efficiently characterizes the intractable entanglement between strongly correlated electrons and phononic modes of unbounded Hilbert space, enabling scalable simulations across broad parameter regimes. In one-dimen… ▽ More We investigate strongly correlated electron-phonon (e-ph) systems via a non-Gaussian matrix product state method. By combining non-Gaussian states with matrix product states, our method efficiently characterizes the intractable entanglement between strongly correlated electrons and phononic modes of unbounded Hilbert space, enabling scalable simulations across broad parameter regimes. In one-dimensional generalized Hubbard--Holstein (HH) models, we identify a pronounced tendency toward phase separation (PS), an instability relevant to recent angle-resolved photoemission spectroscopy observations on doped cuprate chain. In two-dimensional HH models, we construct the phase diagram at half-filling featuring a metallic phase emerging from the competition between non-local phonon-mediated attraction and local Hubbard repulsion. Upon doping, we elucidate the role of soft phonons in stabilizing stripe phases. In the antiferromagnet, the stabilization of the fully filled stripe is attributed to a local retardation effect, wherein the charge order is pinned by phonons, leading to a diminished response to spin fluctuations. In the doped charge-density-wave regime, a novel bipolaronic stripe phase with an enlarged unit cell is stabilized via a non-local retardation effect, where long-range phonon-mediated interactions suppress PS. Our work establishes a systematic route to decoding the e-ph interplay that is crucial for superconductivity. △ Less

Submitted 9 July, 2026; originally announced July 2026.

Unveiling Nanoscale Surface Damage Dynamics in Swift Heavy Ion Irradiated Gallium Nitride

Authors: Jiayu Liang, Shaowei He, Wenlong Liao, Tan Shi, Hang Zang, Yonghong Li, Wenbo Liu, Xiaojun Fu, Chuanjian Yao, Huan He, Jianan Wei, Chaohui He

Abstract: This work systematically unveils the nanoscale surface damage dynamics in gallium nitride by investigating the atomistic mechanisms of hillock formation. The results identify two distinct hillock morphologies dependent on electronic energy loss (Se) values. Bell-shaped hillocks form under 18.2 keV/nm Kr irradiation, whereas crater-rim hillocks with central holes emerge under 40.2 keV/nm Ta irradia… ▽ More This work systematically unveils the nanoscale surface damage dynamics in gallium nitride by investigating the atomistic mechanisms of hillock formation. The results identify two distinct hillock morphologies dependent on electronic energy loss (Se) values. Bell-shaped hillocks form under 18.2 keV/nm Kr irradiation, whereas crater-rim hillocks with central holes emerge under 40.2 keV/nm Ta irradiation. Microstructural analysis reveals that Ga-rich hillocks are accompanied by the generation of metastable zincblende nanodomains. These nanodomains preferentially aggregate around the periphery or sidewalls of the hillocks and exhibit a high spatial correlation with screw dislocations. Further temperature-dependent studies indicate that elevated temperatures significantly enlarge the overall dimensions of the hillock structures without altering their fundamental morphologies. Notably, under Ta irradiation above 1200 K, the high temperatures drastically reduce the viscosity and surface tension of liquid gallium. This enhanced fluidity of the transient molten phase promotes the formation of penetrating nanochannels. △ Less

Submitted 8 July, 2026; originally announced July 2026.

Chiral-Structured Superconductors TrX4 (Tr = Rh, Ir; X = Ge, Si): A Platform for Mixed-Parity Pairing and Topological States

Authors: Zhenhai Yu, Yunguan Ye, Yuwei Zhou, Chaoyang Chu, Congcong Le, Lin Wu, Jian Yuan, Tong Shi, Qingxin Dong, Jinggeng Zhao, Wei Xia, Xiangqi Liu, Xia Wang, Bosen Wang, Jinguang Cheng, Yanhang Ma, Xianxin Wu, Xiangang Wan, Huiqiu Yuan, Yanfeng Guo

Abstract: Chiral-structured superconductors, with simultaneous broken mirror and inversion symmetries, promote unconventional superconductivity through parity-mixing mechanisms. Yet a few bulk chiral-structured superconductors are known, partly due to the difficulty in directly determining their atomic-scale chirality. Here we report three chiral-structured superconductors, , RhGe4, IrGe4, and IrSi4, synthe… ▽ More Chiral-structured superconductors, with simultaneous broken mirror and inversion symmetries, promote unconventional superconductivity through parity-mixing mechanisms. Yet a few bulk chiral-structured superconductors are known, partly due to the difficulty in directly determining their atomic-scale chirality. Here we report three chiral-structured superconductors, , RhGe4, IrGe4, and IrSi4, synthesized under high pressure, with Tc values of about 1.6 K, 1.1 K, and 2.5 K, respectively.Using atomic resolution Cs-corrected scanning transmission electron microscopy (STEM) combined with X-ray diffraction characterizations, we directly confirm their chiral structure (space group P3121). This real space imaging approach overcomes ambiguities in traditional diffraction based methods. These materials exhibit type-II superconductivity, and the enhancement of spin-orbit coupling (SOC) leads to the emergence of mixed parity pairing. Calculations also reveal symmetry protected Weyl points near the Fermi level, which is robust against the SOC. Our work not only expands the family of chiral-structured superconductors but also demonstrates the indispensable role of STEM in directly determining chiral crystal structures. These materials thus offer a clean platform to explore the interplay among structural chirality, SOC, mixed parity superconductivity, and topological quantum phenomena. △ Less

Submitted 7 July, 2026; originally announced July 2026.

Comments: Main Text 28 pages with 5 figures and 1 table; SI 14 pages with 5 figures and 7 tables

Anomalous Structural Response of Quasi-One-Dimensional Antiferromagnetic Metal KMn6Bi5 under high pressure

Authors: Hanming Ma, Qingxin Dong, Tong Shi, Xiaoli Ma, Zhongjin Wu, Shaoheng Ruan, Pengtao Yang, Zhaoming Tian, Jianping Sun, Yoshiya Uwatoko, Genfu Chen, Xiaohui Yu, Bosen Wang, Jinguang Cheng

Abstract: We report high-pressure single-crystal X-ray diffraction measurements on the quasi-one-dimensional (Q1D) antiferromagnetic metal KMn6Bi5 up to 12.5 GPa, revealing the detailed pressure evolution of its atomic coordination environment. We find that the lattice exhibits pronounced anisotropic compressibility-the relative changes in the a and b lattice parameters reach a/a0=0.91 and b/b0 = 0.94 at 12… ▽ More We report high-pressure single-crystal X-ray diffraction measurements on the quasi-one-dimensional (Q1D) antiferromagnetic metal KMn6Bi5 up to 12.5 GPa, revealing the detailed pressure evolution of its atomic coordination environment. We find that the lattice exhibits pronounced anisotropic compressibility-the relative changes in the a and b lattice parameters reach a/a0=0.91 and b/b0 = 0.94 at 12.5 GPa-and a distinct structural anomaly emerges near 11 GPa without any symmetry-breaking. Detailed structural analysis further uncovers an anomalous hardening of the Mn nanotubes between 5 and 11 GPa, followed by a configuration optimization of the Mn/Bi nanotubes around 11 GPa. These features correlate closely with the reported pressure-temperature phase diagram of KMn6Bi5 and compare favorably with the chemical pressure effects induced by substituting K with Na, Rb, or Cs. Our findings provide key microscopic insights into how coordination environment modulation governs the stability of electronic orders in low-dimensional systems. △ Less

Submitted 3 July, 2026; originally announced July 2026.

Comments: 18 pages, 4 figures

Effective potentials for polar molecules under non-orthogonal dual microwave fields

Authors: Fulin Deng, Xinyuan Hu, Su Yi, Tao Shi

Abstract: Dual-microwave shielding has emerged as a powerful tool for stabilizing ultracold polar molecules while tuning their intermolecular interactions. However, the two microwave fields are generally not perfectly orthogonal in experiments. Such misalignment introduces an in-plane component of the linearly polarized microwave, whose frequency differs from that of the elliptically polarized field. This c… ▽ More Dual-microwave shielding has emerged as a powerful tool for stabilizing ultracold polar molecules while tuning their intermolecular interactions. However, the two microwave fields are generally not perfectly orthogonal in experiments. Such misalignment introduces an in-plane component of the linearly polarized microwave, whose frequency differs from that of the elliptically polarized field. This component prevents complete cancellation of the dipole-dipole interaction and, more critically, renders the single-molecule dressed state intrinsically time-dependent, so that the conventional time-independent scattering framework is no longer available. Here we develop a Floquet theory that yields an analytic effective potential and enables accurate scattering calculations for polar molecules in non-orthogonal dual microwave fields. We find that, though misalignment weakens the shielding moderately, inelastic losses remain strongly suppressed under experimentally relevant conditions. Meanwhile, misalignment provides additional tunability of the interaction anisotropy and strength, which has been directly applied to recent experimental observations on the gas-to-droplet transition~[Z. Shi \textit{et al}, arXiv:2508.20518 (2025)] and Fermi-surface deformation in microwave-shielded molecular gases~[S. Biswas \textit{et al}, arXiv:2602.22447]. The framework is not restricted to dual-microwave shielding and can be generalized straightforwardly to arbitrary multi-frequency driving, providing a versatile tool for manipulating ultracold polar molecules under complex microwave configurations. △ Less

Submitted 3 July, 2026; originally announced July 2026.

Comments: 9 pages, 6 figures

Extending Covariant Fluctuation Theorems into Quantum Regime through Quasiprobability Approach

Authors: Ji-Hui Pei, Tingzhang Shi, Jin-Fu Chen, H. T. Quan

Abstract: The covariant formulation of stochastic thermodynamics requires treating the stochastic work as a 4-vector, posing significant challenges for quantum systems due to the non-commutativity. We introduce a new quasiprobability distribution for the work 4-vector, which combines the Wigner and Margenau-Hill quasiprobabilities. This extends the covariant fluctuation theorems from classical to quantum re… ▽ More The covariant formulation of stochastic thermodynamics requires treating the stochastic work as a 4-vector, posing significant challenges for quantum systems due to the non-commutativity. We introduce a new quasiprobability distribution for the work 4-vector, which combines the Wigner and Margenau-Hill quasiprobabilities. This extends the covariant fluctuation theorems from classical to quantum regime. We illustrate our findings with a scalar field driven by classical particles with a generalized version of trace formula. Our work establishes a quasiprobability approach to studying relativistic quantum thermodynamics in a covariant way. △ Less

Submitted 12 June, 2026; originally announced June 2026.

Structural responses incipient to pressure-driven antiferromagnetic quantum critical point of van der Waals heavy-fermion metal CeSiI

Authors: Hanming Ma, Tong Shi, Wenhao Li, Qingxin Dong, Xiaoli Ma, Shaoheng Ruan, Zhongjin Wu, Pengtao Yang, Zhaoming Tian, Jianping Sun, Yoshiya Uwatoko, Xiaohui Yu, Hechang Lei, Bosen Wang, Jinguang Cheng

Abstract: CeSiI is a van der Waals heavy-fermion metal recently found to exhibit unconventional superconductivity near a pressure-induced antiferromagnetic quantum critical point (QCP) at Pc =6 GPa. Here, we report a comprehensive single-crystal X-ray diffraction study of CeSiI under high pressures up to 8.3 GPa at room temperature, revealing subtle structural responses that precede pressure-driven QCP. We… ▽ More CeSiI is a van der Waals heavy-fermion metal recently found to exhibit unconventional superconductivity near a pressure-induced antiferromagnetic quantum critical point (QCP) at Pc =6 GPa. Here, we report a comprehensive single-crystal X-ray diffraction study of CeSiI under high pressures up to 8.3 GPa at room temperature, revealing subtle structural responses that precede pressure-driven QCP. We find that the unit-cell volume decreases smoothly upon compression without showing any structural phase transition in the investigated pressure range. Intriguingly, we observe abrupt and concurrent anisotropic responses of the lattice parameters around Pc =6 GPa, i.e., the a-axis contracts while the c-axis enlongated suddenly, with the unit-cell volume smoothily varies with pressure. Structural refinements further show that these lattice anomalies primarily originate from changes of Ce-Ce and Ce-Si bond lengths, as well as a flattening of the inner honeycomb Si layer within the CeSiI monolayer around Pc. Our findings establish an interesting case linking pressure-driven electronic transition of QCP at low temperatures to incipient structural responses at room temperature, thereby providing fresh insight into the pressure-temperature phase diagram of CeSiI. △ Less

Submitted 10 June, 2026; originally announced June 2026.

Comments: 19 pages, 5 figures

Effective scatterings and universal clusters of heteronuclear ultracold mixtures in quasi-low dimensions

Authors: Tingting Shi, Xiaoling Cui

Abstract: We study the effective s-wave scattering of two heteronuclear atoms harmonically confined in quasi-low dimensions, where the atoms have unequal masses and are subject to different confinement frequencies. The resulting effective scattering parameters in low dimensions, including scattering length and effective range, are derived as functions of three-dimensional scattering parameters and confineme… ▽ More We study the effective s-wave scattering of two heteronuclear atoms harmonically confined in quasi-low dimensions, where the atoms have unequal masses and are subject to different confinement frequencies. The resulting effective scattering parameters in low dimensions, including scattering length and effective range, are derived as functions of three-dimensional scattering parameters and confinement strengths. Using realistic Li-K and Li-Cr mixtures as examples, we further compute the binding energies of universal $(1+N)$ clusters in quasi-low dimensions using the effective scattering parameters. Our findings suggest a promising pathway for practically observing universal clusters and their associated many-body phases in low-dimensional ultracold heteronuclear systems. △ Less

Submitted 1 June, 2026; originally announced June 2026.

Comments: 15 pages, 4 figures

Atomistic Mechanisms of Temperature-Dependent Ion Track Formation in Gallium Nitride under Swift Heavy Ion Irradiation

Authors: Jiayu Liang, Shaowei He, Wenlong Liao, Tan Shi, Hang Zang, Yonghong Li, Xiaojun Fu, Chuanjian Yao, Chaohui He, Jianan Wei, Huan He

Abstract: The radiation tolerance of gallium nitride under extreme conditions is critical for its deployment in next-generation electronic and optoelectronic devices, yet the microscopic mechanisms governing swift heavy ion induced damage at elevated temperatures remain poorly understood. Therefore, this study employs a coupled approach including the two-temperature model and molecular dynamics simulations… ▽ More The radiation tolerance of gallium nitride under extreme conditions is critical for its deployment in next-generation electronic and optoelectronic devices, yet the microscopic mechanisms governing swift heavy ion induced damage at elevated temperatures remain poorly understood. Therefore, this study employs a coupled approach including the two-temperature model and molecular dynamics simulations to resolve the entire processes of ion track generation induced by swift heavy ions irradiation across a wide temperature range. A temperature-driven morphological transition of ion tracks, evolving from discontinuous segments to continuous tracks composed of isolated nanobubbles, and ultimately to fully continuous channels is observed. Under lower electronic stopping loss of 430 MeV Kr irradiation, increasing temperature significantly enhances track visibility, enlarges track radii and promotes nanobubble formation. For higher electronic stopping conditions of 1171 MeV Ta irradiation, continuous ion tracks consisting of discontinuous nanobubbles (~1.5 nm radius) emerge already at 300 K, followed by a thermally activated transition into continuous channels with further radial expansion. At the atomic scale, SHI irradiation induces decomposition of wurtzite GaN into Ga clusters and N2 molecules along the ion trajectory, with Ga-rich regions and recrystallized wurtzite phases accumulating near bubble interfaces, while N2 preferentially segregates within bubble cores. Additionally, zincblende nanodomains nucleate around ion tracks and exhibit strong spatial correlation with radiation-induced dislocation networks, particularly screw dislocations, providing potential pathways for leakage current and increased susceptibility to single-event burnout. △ Less

Submitted 27 April, 2026; originally announced April 2026.

Cs$_3$V$_9$Te$_{13}$: A Correlated Electron System with Topological Flat Bands

Authors: Chang-Chao Liu, Ji-Yong Liu, Jing Li, Hua-Xun Li, Jia-Yi Lu, Tong Shi, Qing-Xin Dong, Gen Li, Bo-Sen Wang, Yi Liu, Jin-Guang Cheng, Guang-Han Cao

Abstract: Correlated electron systems with topological flat bands show great promise in exploring exotic quantum phenomena. However, such crystalline materials remain rare. Here we report the discovery of a novel material, Cs$_3$V$_9$Te$_{13}$, which unexpectedly exhibits magnetism and significant electron correlations. The crystal structure features two interpenetrating sets of vanadium triangles that can… ▽ More Correlated electron systems with topological flat bands show great promise in exploring exotic quantum phenomena. However, such crystalline materials remain rare. Here we report the discovery of a novel material, Cs$_3$V$_9$Te$_{13}$, which unexpectedly exhibits magnetism and significant electron correlations. The crystal structure features two interpenetrating sets of vanadium triangles that can be linked with an ideal kagome lattice. The physical property measurements demonstrate a cascade of correlated electron phenomena, including quasi-two-dimensional bad metal, non-Fermi-liquid behavior, antiferromagnetic spin-density-wave transition at $T_\mathrm{N}$ = 47 K, possible short-range spin ordering at $\sim$350 K, a large Sommerfeld coefficient of 246 mJ mol-fu$^{-1}$ K$^{-2}$, and pressure-induced quantum criticality. These correlated electron behaviors are associated with the topological flat bands at the Fermi level, the latter of which are generated from the V2 sublattice in terms of a bipartite kagome model. Our findings establish Cs$_3$V$_9$Te$_{13}$ as a brand new correlated matter that synergistically combines flat-band physics and tunable properties. △ Less

Submitted 29 March, 2026; originally announced March 2026.

Comments: 23 pages, 9 figures, 2 tables

Controlled symmetry breaking of the Fermi surface in ultracold polar molecules

Authors: Shrestha Biswas, Sebastian Eppelt, Weikun Tian, Wei Zhang, Fulin Deng, Christine Frank, Tao Shi, Immanuel Bloch, Xin-Yu Luo

Abstract: Long-range anisotropic dipole-dipole interactions between ultracold polar molecules are predicted to drive exotic quantum phases, yet direct many-body signatures of these interactions in degenerate Fermi gases have remained elusive. Here, we report the observation of an interaction-induced controlled deformation of the Fermi surface, providing a clear many-body signature in a deeply degenerate Fer… ▽ More Long-range anisotropic dipole-dipole interactions between ultracold polar molecules are predicted to drive exotic quantum phases, yet direct many-body signatures of these interactions in degenerate Fermi gases have remained elusive. Here, we report the observation of an interaction-induced controlled deformation of the Fermi surface, providing a clear many-body signature in a deeply degenerate Fermi gas of $^{23}\text{Na}^{40}\text{K}$ molecules. Using double microwave (MW) shielding, we prepare $8 \times 10^3$ molecules at $0.23(1)$ times the Fermi temperature, achieving a three-fold suppression of inelastic losses compared to single MW shielding while preserving strong elastic dipolar scattering. We observe Fermi surface deformations of up to $7\,\%$, more than two times larger than those observed in magnetic atoms, despite operating at two orders of magnitude lower densities. Crucially, we demonstrate continuous tuning of the interaction potential from axial U(1) to biaxial C$_{2}$ symmetry, directly imprinting this geometry onto the Fermi surface. We find excellent agreement between our experimental results and parameter-free Hartree-Fock theory. These results establish MW-shielded polar molecules as a highly tunable platform for exploring strongly correlated dipolar Fermi matter and offer a promising path towards topological superfluidity. △ Less

Submitted 25 February, 2026; originally announced February 2026.

Comments: 15 pages, 10 figures

Phase diagram of the single-flavor Gross--Neveu--Wilson model from the Grassmann corner transfer matrix renormalization group

Authors: Jian-Gang Kong, Shinichiro Akiyama, Tao Shi, Z. Y. Xie

Abstract: We investigate the phase structure of the single-flavor Gross--Neveu model with Wilson fermions using the Grassmann corner transfer matrix renormalization group (CTMRG). The path integral is formulated as a two-dimensional Grassmann tensor network and approximately contracted by the Grassmann CTMRG algorithm. We investigate the phase diagram by varying the fermion mass and the four-fermion couplin… ▽ More We investigate the phase structure of the single-flavor Gross--Neveu model with Wilson fermions using the Grassmann corner transfer matrix renormalization group (CTMRG). The path integral is formulated as a two-dimensional Grassmann tensor network and approximately contracted by the Grassmann CTMRG algorithm. We investigate the phase diagram by varying the fermion mass and the four-fermion coupling, using the pseudoscalar condensate as an order parameter for the $\mathbb{Z}_{2}$ parity symmetry breaking phase. The universality classes of the phase boundaries are identified through the central charge $c$ obtained via scaling analysis of the entanglement entropy. Furthermore, we extract the quantity related to the entanglement spectrum from the converged CTMRG environments, allowing us to distinguish the topological insulator phase and the trivial phase. The resulting phase structure suggests that the Aoki phase is separated from the other phases by critical lines characterized by $c=1/2$, while the critical lines with $c=1$ separate the topological insulating and trivial phases. Our numerical results also indicate that the Aoki phase does not persist in the strong-coupling regime for the single-flavor theory. △ Less

Submitted 10 June, 2026; v1 submitted 25 February, 2026; originally announced February 2026.

Comments: 26 pages, 20 figures

Report number: UTHEP-816, UTCCS-P-174

Journal ref: Phys. Rev. D 113, 114504(2026)

Anisotropic Core-Shell Swift Heavy Ion Tracks in beta-Ga2O3

Authors: Huan He, Jiayu Liang, Shaowei He, Yanwen Zhang, Jiahui Zhang, Ziqi Cai, Tan Shi, Hang Zang, Flyura Djurabekova, Chaohui He, Junlei Zhao

Abstract: Swift heavy ion (SHI) irradiation generates nanoscale ion tracks through intense electronic excitation, yet the microscopic mechanisms governing their morphology and phase stability in low symmetry oxides remain poorly understood. Here, a multiscale atomistic simulation framework is used to investigate the formation and recovery of SHI-induced tracks in monoclinic $β$-Ga2O3 over a wide range of el… ▽ More Swift heavy ion (SHI) irradiation generates nanoscale ion tracks through intense electronic excitation, yet the microscopic mechanisms governing their morphology and phase stability in low symmetry oxides remain poorly understood. Here, a multiscale atomistic simulation framework is used to investigate the formation and recovery of SHI-induced tracks in monoclinic $β$-Ga2O3 over a wide range of electronic energy losses (Se) and crystallographic orientations. A sequence of distinct structural responses is identified with increasing Se: (i) complete lattice recovery at low Se; (ii) recrystallization into a metastable $γ$-Ga2O3 phase at intermediate Se; and (iii) the formation of core-shell ion tracks at high Se, consisting of an amorphous core surrounded by a recrystallized $γ$-phase shell. Despite the essentially isotropic initial energy deposition, the final ion-track morphology exhibits pronounced crystallographic anisotropy, governed by orientation-dependent recovery dynamics. The superior recrystallization along the [010] direction is attributed to its exceptionally high elastic stiffness. Notably, SHI irradiation perpendicular to the (100) plane induces a more severe structural response at low Se ($\le$ 10 keV/nm), however, at higher Se, it yields a smaller residual ion track compared to the other orientations. The simulated ion-track sizes show excellent quantitative agreement with the available experimental measurements over a wide range of Se values. These findings establish a unified atomic-scale picture of core-shell track formation and anisotropic recovery in $β$-Ga2O3. △ Less

Submitted 1 June, 2026; v1 submitted 14 February, 2026; originally announced February 2026.

Superconductivity under pressure in the two-dimensional van der Waals heavy-fermion metal CeSiI

Authors: Tong Shi, Wenhao Li, Qingxin Dong, Pengtao Yang, Hanming Ma, Zhaoming Tian, Ningning Wang, Jianping Sun, Yoshiya Uwatoko, Yi-feng Yang, Bosen Wang, Hechang Lei, Jinguang Cheng

Abstract: CeSiI is a newly discovered exfoliable van der Waals (vdW) heavy-fermion metal featured by a long-range antiferromagnetic (AF) order (TN =7.5 K) inside the Kondo coherent state below T* = 50 K. To gain a more profound understanding of the intriguing physics of this material and to uncover novel phenomena driven by quantum criticality, it is imperative to construct the phase diagram of CeSiI detail… ▽ More CeSiI is a newly discovered exfoliable van der Waals (vdW) heavy-fermion metal featured by a long-range antiferromagnetic (AF) order (TN =7.5 K) inside the Kondo coherent state below T* = 50 K. To gain a more profound understanding of the intriguing physics of this material and to uncover novel phenomena driven by quantum criticality, it is imperative to construct the phase diagram of CeSiI detailing the evolutions of T* and TN as a function of external tuning parameters such as pressure (P).In this study, we employ high pressure as an effective tuning knob to investigate this system, thereby generating a comprehensive T-P phase diagram of CeSiI. This diagram is characterized by an unusual V-shaped nonmonotonic evolution of T*(P) and the emergence of a superconducting dome with Tcmax = 240 mK upon suppression of AF order at Pc = 6 GPa, coinciding with the minimum of T*(P).The close proximity of the superconductivity (SC) to the AF instability and an unusually large upper critical field Bc2(0) exceeding 4-7 times the Pauli paramagnetic limit, suggests an unconventional pairing mechanism in CeSiI. Further analyses of normal-state transport properties provide evidence of quantum criticality, i.e., non-Fermi-liquid behavior and divergence of quasiparticle effective mass near Pc = 7 GPa. Our findings not only establish CeSiI as the first vdW heavy-fermion superconductor but also highlight an unconventional nature for the Kondo coherent state at T* at ambient pressure, hence opening a new avenue to study the interplay of strong electron correlation, Kondo hybridization, magnetism, and unconventional SC in the vdW heavy-fermion systems. △ Less

Submitted 26 January, 2026; v1 submitted 26 January, 2026; originally announced January 2026.

Comments: 13 pages, 4 figures

Visualizing the dispersions of Fermi polaron and molecule via spin-orbit coupling

Authors: Tingting Shi, Xiaoling Cui

Abstract: We propose to measure the dispersions of Fermi polaron and molecule by engineering spin-orbit coupling (SOC) on the impurity, which induces spin flip with finite momentum transfer. The polaron dispersion can be probed at small SOC momentum from the linear response of impurity spin. For molecule, we show that it can be prepared through an adiabatic steady-state evolution when setting SOC momentum a… ▽ More We propose to measure the dispersions of Fermi polaron and molecule by engineering spin-orbit coupling (SOC) on the impurity, which induces spin flip with finite momentum transfer. The polaron dispersion can be probed at small SOC momentum from the linear response of impurity spin. For molecule, we show that it can be prepared through an adiabatic steady-state evolution when setting SOC momentum as the Fermi momentum of majority bath. By gradually reducing SOC strength to zero, the steady state smoothly evolves to a molecular state with directional symmetry breaking. The corresponding dispersion can then be probed experimentally through the center-of-mass momentum distribution of molecules at finite density. Our scheme reveals a fundamental momentum difference between Fermi polaron and molecule, thereby offering a clear physical picture for their first-order transition in single-impurity system. △ Less

Submitted 29 December, 2025; originally announced December 2025.

Comments: 5+ pages, 4 figures

Breaking the 800 mV open-circuit voltage barrier in antimony sulfide photovoltaics

Authors: Jiacheng Zhou, Xinwei Wang, Tianle Shi, Lei Wan, Junzhi Ye, Zhiqiang Li, Aron Walsh, Robert L. Z. Hoye, Ru Zhou

Abstract: Sb2S3 is a promising material for low-toxicity, high-stability next-generation photovoltaics. Despite high optical limits in efficiency, progress in improving its device performance has been limited by severe voltage losses. Recent spectroscopic investigations suggest that self-trapping occurs in Sb2S3, limiting the open-circuit voltage (Voc) to a maximum of approximately 800 mV, which is the leve… ▽ More Sb2S3 is a promising material for low-toxicity, high-stability next-generation photovoltaics. Despite high optical limits in efficiency, progress in improving its device performance has been limited by severe voltage losses. Recent spectroscopic investigations suggest that self-trapping occurs in Sb2S3, limiting the open-circuit voltage (Voc) to a maximum of approximately 800 mV, which is the level the field has asymptotically approached. In this work, we surpass this voltage barrier through reductions in the defect density in Sb2S3 thin films by modulating the growth mechanism in chemical bath deposition using citrate ligand additives. Deep level transient spectroscopy identifies two deep traps 0.4-0.7 eV above the valence band maximum, and, through first-principles calculations, we identify these to likely be S vacancies, or Sb on S anti-sites. The concentrations of these traps are lowered by decreasing the grain boundary density from 1114+/-52 nm/um2 to 585+/-10 nm/um2, and we achieve a Voc of 824 mV, the record for Sb2S3 solar cells. This work addresses the debate in the field around whether Sb2S3 is limited by defects or self-trapping, showing that it is possible to improve the performance towards the radiative limit through careful defect engineering. △ Less

Submitted 19 December, 2025; originally announced December 2025.

Comments: 29 pages, 6 figures

Exact four-vector work distribution and covariant fluctuation theorems of work for a relativistic particle in an expanding piston

Authors: Tingzhang Shi, Chentong Qi, H. T. Quan

Abstract: We investigate the non-equilibrium four-vector work in an expanding relativistic piston. We derive the exact work distribution in this pedagogical model and find that the joint distribution of four-vector work $(W^0, W^1)$ concentrates on the origin and some curves in the $(W^0, W^1)$ space, rather than being smoothly distributed. In the non-relativistic limit, our model consistently recovers the… ▽ More We investigate the non-equilibrium four-vector work in an expanding relativistic piston. We derive the exact work distribution in this pedagogical model and find that the joint distribution of four-vector work $(W^0, W^1)$ concentrates on the origin and some curves in the $(W^0, W^1)$ space, rather than being smoothly distributed. In the non-relativistic limit, our model consistently recovers the non-relativistic dynamics. We further demonstrate that the momentum component of four-vector work remains significant in both the Lorentz-relativistic and Galilean-relativistic frameworks. On top of the work distribution, we verify a family of covariant fluctuation theorems of work. In addition, we introduce a novel geometrical technique for analyzing the dynamics of relativistic collision processes, which can be straightforwardly extended to multi-dimensional piston models. △ Less

Submitted 8 May, 2026; v1 submitted 27 November, 2025; originally announced November 2025.

Comments: 19 pages, 15 figures

Interaction-induced Dimension Reduction for Bound States in Microwave-Shielded Ultracold Molecules

Authors: Haitian Wang, Tingting Shi, Xiaoling Cui

Abstract: We investigate tetratomic and hexatomic bound states of ultracold molecules dressed by an elliptic microwave field. We show that these bound states can be accurately described by effective one-dimensional (1D) models incorporating high-order angular fluctuations, despite the physical system is in three-dimensional (3D) free space. By comparing with exact solutions of the full 3D system, we identif… ▽ More We investigate tetratomic and hexatomic bound states of ultracold molecules dressed by an elliptic microwave field. We show that these bound states can be accurately described by effective one-dimensional (1D) models incorporating high-order angular fluctuations, despite the physical system is in three-dimensional (3D) free space. By comparing with exact solutions of the full 3D system, we identify the validity region of such 1D description in the parameter plane of ellipticity and coupling strength of microwave field. The hard-core character of these effective models enables a duality between bosonic and fermionic molecules in real and spectral space, while their momentum distributions remain distinct. Our results have demonstrated an effective dimension reduction in microwave-shielded molecular systems, which is purely due to the intrinsic interaction anisotropy rather than any external confinement. Extending to large systems, our results suggest a self-bound single-molecule array as the ground state of both bosonic and fermionic molecular gases. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: 13 pages, 8 figures

Thermal Tensor Network Simulations of Lattice Fermions with Fixed Filling

Authors: Qiaoyi Li, Dai-Wei Qu, Bin-Bin Chen, Tao Shi, Wei Li

Abstract: Numerical simulations of strongly correlated fermions at finite temperature are essential for studying high-temperature superconductivity and other quantum many-body phenomena. The recently developed tangent-space tensor renormalization group (tanTRG) provides an efficient and accurate framework by representing thermal density operators as matrix product operators. However, the particle number gen… ▽ More Numerical simulations of strongly correlated fermions at finite temperature are essential for studying high-temperature superconductivity and other quantum many-body phenomena. The recently developed tangent-space tensor renormalization group (tanTRG) provides an efficient and accurate framework by representing thermal density operators as matrix product operators. However, the particle number generally varies during the cooling process. The conventional strategy of fine-tuning chemical potentials to reach a target filling is computationally demanding. Here we propose a fixed-$N$ tanTRG algorithm that stabilizes the average particle number by adaptively tuning the chemical potential within the imaginary-time evolution. We benchmark its accuracy on exactly solvable free fermions, and further apply it to the square-lattice Hubbard model. For hole-doped cases, we study the temperature evolution of charge and spin correlations, identifying several characteristic temperature scales for stripe formation. Our results establish fixed-$N$ tanTRG as an efficient and reliable tool for finite-temperature studies of correlated fermion systems. △ Less

Submitted 1 March, 2026; v1 submitted 10 November, 2025; originally announced November 2025.

Comments: 8 pages, 8 figures, comments are welcome

Journal ref: Phys. Rev. B 113, 085150 (2026)

Impurity-induced topological decomposition

Authors: Tianxing Shi, Chuhang Zhang, Liang Jin, Linhu Li

Abstract: Controlling topological phases is a central goal in quantum materials and related fields, enabling applications such as robust transport and programmable edge states. Here we uncover a mechanism in which local on-site impurities act as knobs to decompose global topological properties in discrete steps. In non-Hermitian lattices with spectral winding topology, we show that each impurity sequentiall… ▽ More Controlling topological phases is a central goal in quantum materials and related fields, enabling applications such as robust transport and programmable edge states. Here we uncover a mechanism in which local on-site impurities act as knobs to decompose global topological properties in discrete steps. In non-Hermitian lattices with spectral winding topology, we show that each impurity sequentially reduces the winding number by one, which is directly manifested as a stepwise decomposition of quantized plateaus in the steady-state response. Based on this principle, we further develop a scheme that sequentially induces topological edge states under impurity control, in a class of Hermitian topological systems constructed by doubling the non-Hermitian ones. Our findings reveal a general scheme to tune global topological properties with local perturbations, establishing a universal framework for impurity-controlled topological phases and offering a foundation for future exploration of reconfigurable topological phenomena across diverse physical platforms. △ Less

Submitted 24 October, 2025; originally announced October 2025.

Comments: 18 pages, 11 figures, comments are welcome

Consistent gauge theories for the slave particle representation of the strongly correlated $t$-$J$ model

Authors: Xi Luo, Tao Shi, Yue Yu, Long Liang

Abstract: We aim to clarify the confusion and inconsistency in our recent works [1,2], and to address the incompleteness therein. In order to avoid the ill-defined nature of the free propagator of the gauge field in the ordered states of the $t$-$J$ model, we adopted a gauge fixing that was not of the Becchi-Rouet-Stora-Tyutin (BRST) exact form in our previous work [2]. This led to the situation where Dirac… ▽ More We aim to clarify the confusion and inconsistency in our recent works [1,2], and to address the incompleteness therein. In order to avoid the ill-defined nature of the free propagator of the gauge field in the ordered states of the $t$-$J$ model, we adopted a gauge fixing that was not of the Becchi-Rouet-Stora-Tyutin (BRST) exact form in our previous work [2]. This led to the situation where Dirac's second-class constraints, namely, the slave particle number constraint and the Ioffe-Larkin current constraint, were not rigorously obeyed. Here we show that a consistent gauge fixing condition that enforces the exact constraints is BRST-exact in our theory. An example is the Lorenz gauge. On the other hand, we prove that although the free propagator of the gauge field in the Lorenz gauge is ill-defined, the full propagator is still well-defined. This implies that the strongly correlated $t$-$J$ model can be exactly mapped to a perturbatively controllable theory within the slave particle representation. △ Less

Submitted 19 January, 2026; v1 submitted 10 October, 2025; originally announced October 2025.

Comments: 9 pages

Journal ref: Commun. Theor. Phys. 78 045704 (2026)

Tetratomic states of microwave dressed and associated ultracold 23Na40K molecules

Authors: Zhengyu Gu, Xuansheng Zhou, Wei Chen, Wei Han, Fulin Deng, Tao Shi, Pengjun Wang, Jing Zhang

Abstract: Ultracold diatomic molecules have achieved significant breakthroughs in recent years, enabling the exploration of quantum chemistry, precision measurements, and strongly correlated many-body physics. Extending ultracold molecular complexity to polyatomic molecules, such as triatomic and tetratomic molecules, has attracted considerable interest. However, the realization of ultracold polyatomic mole… ▽ More Ultracold diatomic molecules have achieved significant breakthroughs in recent years, enabling the exploration of quantum chemistry, precision measurements, and strongly correlated many-body physics. Extending ultracold molecular complexity to polyatomic molecules, such as triatomic and tetratomic molecules, has attracted considerable interest. However, the realization of ultracold polyatomic molecules remains technically challenging due to their complex energy-level structures. While only a few experiments have successfully demonstrated the formation of polyatomic molecules by magnetoassociation or electroassociation, here we present the first step toward producing tetratomic molecules through the development of a microwave association technique combined with microwave dressing. When the two lowest rotational states of the molecules are dressed by a microwave field, weakly bound tetramer states emerge in the entrance channel with free dark excited states $\ket{0}$ and a dressed state $\ket{+}$. The spectroscopy of these weakly bound tetramers is probed by another microwave field that drives transitions from the populated dressed states $\ket{+}$. By precisely discriminating the complex hyperfine structure of the dark excited level $\ket{0}$ from the dressed-state spectroscopy, the binding energy of the tetratomic molecules is measured and characterized. Our work contributes to the understanding of complex few-body physics within a system of microwave-dressed molecules and may open an avenue toward the creation and control of ultracold polyatomic molecules. △ Less

Submitted 28 September, 2025; originally announced September 2025.

Comments: 11 pages, 8 figures

Bose-Einstein condensate of ultracold sodium-rubidium molecules with tunable dipolar interactions

Authors: Zhaopeng Shi, Zerong Huang, Fulin Deng, Wei-Jian Jin, Su Yi, Tao Shi, Dajun Wang

Abstract: Realizing Bose-Einstein condensation of polar molecules is a long-standing challenge in ultracold physics and quantum science due to near-universal two-body collisional losses. Here, we report the production of a Bose-Einstein condensate of ground-state sodium-rubidium molecules via high efficiency evaporative cooling, with losses suppressed using the dual microwave shielding technique. The abilit… ▽ More Realizing Bose-Einstein condensation of polar molecules is a long-standing challenge in ultracold physics and quantum science due to near-universal two-body collisional losses. Here, we report the production of a Bose-Einstein condensate of ground-state sodium-rubidium molecules via high efficiency evaporative cooling, with losses suppressed using the dual microwave shielding technique. The ability to tune the dipolar interaction between these ultracold polar molecules is crucial for producing the condensate and enables exciting prospects for future applications. We explore different regimes of dipolar interactions, realizing both the gas phase and the quantum droplet phase of the molecular condensate. This work opens new avenues for investigating quantum matter with strong dipolar interactions and for quantum simulation of long-range many-body systems. △ Less

Submitted 28 August, 2025; originally announced August 2025.

Comments: 13 pages, 8 fugures

Supersolid Phases in Ultracold Gases of Microwave Shielded Polar Molecules

Authors: Wei Zhang, Hongye Liu, Fulin Deng, Kun Chen, Su Yi, Tao Shi

Abstract: We propose a novel scheme to realize the supersolid phase in ultracold gases of microwave-shielded polar molecules by engineering an additional anisotropy in inter-molecular dipolar interaction via an elliptically polarized microwave. It is shown through quantum Monte-Carlo calculations that the interplay of the anisotropies between the interaction and trapping potential gives rise to rich quantum… ▽ More We propose a novel scheme to realize the supersolid phase in ultracold gases of microwave-shielded polar molecules by engineering an additional anisotropy in inter-molecular dipolar interaction via an elliptically polarized microwave. It is shown through quantum Monte-Carlo calculations that the interplay of the anisotropies between the interaction and trapping potential gives rise to rich quantum phases. Particularly, it is found that the supersolid phase emerges in the parameter regime accessible to current experiments. Our study paves the way for exploring the properties of supersolid phases in ultracold gases of polar molecules. △ Less

Submitted 30 June, 2025; originally announced June 2025.

Pseudo-Goldstone Modes at Finite Temperature

Authors: Xiyue Lin, Tao Shi

Abstract: Goldstone's theorem and its extension to pseudo-Goldstone (PG) modes have profound implications across diverse areas of physics, from quantum chromodynamics to quantum magnetism. PG modes emerge from accidental degeneracies lifted by quantum and thermal fluctuations, leading to a finite gap--a phenomenon known as "order by disorder." In this paper, we derive a general curvature formula for the PG… ▽ More Goldstone's theorem and its extension to pseudo-Goldstone (PG) modes have profound implications across diverse areas of physics, from quantum chromodynamics to quantum magnetism. PG modes emerge from accidental degeneracies lifted by quantum and thermal fluctuations, leading to a finite gap--a phenomenon known as "order by disorder." In this paper, we derive a general curvature formula for the PG gap at finite temperature, applicable to both collinear (e.g., ferromagnets and anti-ferromagnets) and noncollinear magnetic orders (e.g., coplanar orders in frustrated magnetic systems). After validating our formula against known models, we apply it to the XXZ model on the triangular lattice, which hosts coplanar magnetic orders in equilibrium and is relevant to materials such as Na2BaCo(PO4)2 and K2Co(SeO3)2, known for their supersolid phases and giant magnetocaloric effects. Our results reveal a distinct scaling behavior: a linear decrease of the PG gap with temperature, driven by entropy effects from magnon scattering across multiple bands. This stands in stark contrast to the high-temperature scaling recently proposed for systems with a single magnon band. This work establishes a general framework for investigating PG modes at finite temperatures and opens an avenue to explore rich quantum phases and dynamics in frustrated systems with noncollinear magnetic orders. △ Less

Submitted 12 May, 2025; originally announced May 2025.

Universal Bound States with Bose-Fermi Duality in Microwave-Shielded Polar Molecules

Authors: Tingting Shi, Haitian Wang, Xiaoling Cui

Abstract: We report universal bound states of microwave-shielded ultracold molecules that solely depend on the strengths of long-range dipolar interaction and microwave coupling. Under a highly elliptic microwave field, few-molecule scatterings in three dimension are shown to be governed by effective one-dimensional (1D) models, which well reproduce the tetratomic bound state and the Born-Oppenheimer potent… ▽ More We report universal bound states of microwave-shielded ultracold molecules that solely depend on the strengths of long-range dipolar interaction and microwave coupling. Under a highly elliptic microwave field, few-molecule scatterings in three dimension are shown to be governed by effective one-dimensional (1D) models, which well reproduce the tetratomic bound state and the Born-Oppenheimer potential in three-molecule sector. For hexatomic systems comprising three identical molecules, we find much deeper bound state than the tetratomic one, with binding energy exceeding twice of the latter. Strikingly, these bound states display Bose-Fermi duality as facilitated by the effective 1D scattering with a large repulsive core from angular fluctuations. For large molecule ensembles, our results suggest the formation of elongated self-bound droplets with crystalline patterns in both bosonic and fermionic molecules. △ Less

Submitted 27 January, 2026; v1 submitted 30 April, 2025; originally announced April 2025.

Comments: 7+9 pages, 5+7 figures; Further improvement of effective 1D model (with high-order angular fluctuations) for small microwave ellipticity can be found in 2511.09856

Journal ref: Phys. Rev. Lett. 136, 043402 (2026)

Attractive and repulsive angulons in superfluid environments

Authors: Wei Zhang, Zhongda Zeng, Tao Shi

Abstract: We investigate the in- and out-of-equilibrium phenomena of a rotational impurity -- specifically, a linear molecule -- coupled to a nonconventional environment, a helium nanodroplet. By employing a Lee-Low-Pines-like transformation combined with a multireference configuration approach, we self-consistently account for the molecule's backaction on the superfluid bath and accurately capture the comp… ▽ More We investigate the in- and out-of-equilibrium phenomena of a rotational impurity -- specifically, a linear molecule -- coupled to a nonconventional environment, a helium nanodroplet. By employing a Lee-Low-Pines-like transformation combined with a multireference configuration approach, we self-consistently account for the molecule's backaction on the superfluid bath and accurately capture the complex entanglement between the molecule's rotational degrees of freedom and the bath excitations. Our findings reveal that, in the ground state, the impurity induces a density defect in the superfluid bath, giving rise to two novel types of excited states: (a) attractive angulon states, analogous to bound states in photonic crystals and Yu-Shiba-Rusinov bound states in superconductors, localized within the density defect region; and (b) long-lived repulsive angulon states in dilute environments. Rotational spectroscopy demonstrates a crossover from repulsive to attractive angulon states as the bath density increases. This work paves the way for exploring novel nonequilibrium phenomena of quantum impurities in interacting environments. △ Less

Submitted 22 April, 2025; originally announced April 2025.

Comments: 7 pages, 4 figures

Journal ref: Phys. Rev. A 111, 043317 (2025)

Quantum Phases for Finite-Temperature Gases of Bosonic Polar Molecules Shielded by Dual Microwaves

Authors: Wei Zhang, Kun Chen, Su Yi, Tao Shi

Abstract: We investigate the finite-temperature phase diagram of polar molecules shielded by dual microwave fields using the path integral Monte Carlo method combined with the worm algorithm. We determine the critical temperature $T_c$ for Bose-Einstein condensations (BECs) and identify two distinct phases below $T_c$: the expanding gas (EG) phase and the self-bound gas (SBG) phase. We further analyze the t… ▽ More We investigate the finite-temperature phase diagram of polar molecules shielded by dual microwave fields using the path integral Monte Carlo method combined with the worm algorithm. We determine the critical temperature $T_c$ for Bose-Einstein condensations (BECs) and identify two distinct phases below $T_c$: the expanding gas (EG) phase and the self-bound gas (SBG) phase. We further analyze the temperature and interaction-strength dependence of the condensate and superfluid fractions. Notably, in contrast to dilute atomic BECs, the SBG phase displays a low condensate fraction and a high superfluid fraction, resembling the behavior of strongly correlated $^4$He superfluids. These significant many-body correlations arise from the interplay between long-range dipole-dipole interactions and the short-range shielding potential. Furthermore, we demonstrate that the aspect ratio of the gas provides a characteristic geometric signature to accurately determine the EG-to-SBG transition, robust against external trapping potentials. Our findings provide unbiased and numerically exact results to guide upcoming experiments with polar molecules. △ Less

Submitted 4 March, 2025; originally announced March 2025.

Kondo impurity in an attractive Fermi-Hubbard bath: Equilibrium and dynamics

Authors: Zhi-Yuan Wei, Tao Shi, J. Ignacio Cirac, Eugene A. Demler

Abstract: We investigate theoretically equilibrium and dynamical properties of a Kondo impurity coupled to either 1D or 2D superconductors, modeled by the attractive Fermi-Hubbard model. By employing a non-Gaussian variational approach, we go beyond the approximation of a constant superconducting (SC) gap. We show that dynamical properties of the system can be modified qualitatively, when space and time dep… ▽ More We investigate theoretically equilibrium and dynamical properties of a Kondo impurity coupled to either 1D or 2D superconductors, modeled by the attractive Fermi-Hubbard model. By employing a non-Gaussian variational approach, we go beyond the approximation of a constant superconducting (SC) gap. We show that dynamical properties of the system can be modified qualitatively, when space and time dependent renormalization of the SC gap and electron-impurity hybridization are included. For the ground state, we find the singlet-doublet phase transition and $π$-phase shifts of the SC order parameter. For dynamics, first we consider spin dynamics following an abrupt connection of the polarized impurity to the 2D bath. We find rapid relaxation of impurity polarization and directional emission of a magnetization pulse, which becomes damped as it propagates into the bulk. Then we analyze transport between two SC leads coupled through the impurity at finite bias voltage. Here we go beyond analysis of the steady state to investigate full-time dynamics following an abrupt application of the bias voltage. We uncover four distinct regimes in the transient dynamics and transport properties: (I) the AC Josephson effect regime; (II) dynamical competition between charge-density-wave (CDW) and SC orders with transient Kondo correlations; (III) the coexistence of AC and DC currents facilitated by partial Kondo screening and dynamical stabilization of the SC order; (IV) DC Kondo transport regime modified by the SC order. Regime II exhibits a dynamical transition from SC to CDW order that locally restores the U(1) symmetry. We argue that our findings for regime IV provide a theoretical explanation for the experimentally observed anomalous enhancement of DC conductance and suppression of the AC Josephson current. Finally, we discuss the potential experimental realization with ultracold atoms. △ Less

Submitted 9 January, 2025; originally announced January 2025.

Comments: 27 pages, 13 figures. The abstract on the arXiv website is slightly shorter than the PDF version due to the length limit set by arXiv

Two- and many-body physics of ultracold molecules dressed by dual microwave fields

Authors: Fulin Deng, Xinyuan Hu, Wei-Jian Jin, Su Yi, Tao Shi

Abstract: We investigate the two- and many-body physics of the ultracold polar molecules dressed by dual microwaves with distinct polarizations. Using Floquet theory and multichannel scattering calculations, we identify a regime with the largest elastic-to-inelastic scattering ratio which is favorable for performing evaporative cooling. Furthermore, we derive and, subsequently, validate an effective interac… ▽ More We investigate the two- and many-body physics of the ultracold polar molecules dressed by dual microwaves with distinct polarizations. Using Floquet theory and multichannel scattering calculations, we identify a regime with the largest elastic-to-inelastic scattering ratio which is favorable for performing evaporative cooling. Furthermore, we derive and, subsequently, validate an effective interaction potential that accurately captures the dynamics of microwave-shielded polar molecules (MSPMs). We also explore the ground-state properties of the ultracold gases of MSPMs by computing physical quantities such as gas density, condensate fraction, momentum distribution, and second-order correlation. It is shown that the system supports a weakly correlated expanding gas state and a strongly correlated self-bound gas state. Since the dual-microwave scheme introduces addition control knob and is essential for creating ultracold Bose gases of polar molecules, our work pave the way for studying two- and many-body physics of the ultracold polar molecules dressed by dual microwaves. △ Less

Submitted 15 January, 2025; v1 submitted 9 January, 2025; originally announced January 2025.

Strong superconducting pairing strength and pseudogap features in a putative multiphase heavy-fermion superconductor CeRh2As2 by soft point-contact spectroscopy

Authors: Qingxin Dong, Tong Shi, Pengtao Yang, Xinyang Liu, Xiaofan Shi, Lei Wang, Junsen Xiang, Hanming Ma, Zhaoming Tian, Jianping Sun, Yoshiya Uwatoko, Genfu Chen, Xinbo Wang, Jie Shen, Rui Wu, Xin Lu, Peijie Sun, Grzegorz Chajewski, Dariusz Kaczorowski, Bosen Wang, Jinguang Cheng

Abstract: CeRh2As2 is a newly discovered candidate of multiphase heavy-fermion superconductor (Tc=0.3 K) with intriguing physical properties. Here, we employ soft point-contact spectroscopy to investigate its energy gap behaviors in both the normal and superconducting states. The differential conductance below Tc reveals an estimated superconducting energy gap of 2ΔSC=0.24 meV and thus an extremely strong s… ▽ More CeRh2As2 is a newly discovered candidate of multiphase heavy-fermion superconductor (Tc=0.3 K) with intriguing physical properties. Here, we employ soft point-contact spectroscopy to investigate its energy gap behaviors in both the normal and superconducting states. The differential conductance below Tc reveals an estimated superconducting energy gap of 2ΔSC=0.24 meV and thus an extremely strong superconducting pairing strength 2ΔSC/kBTc=8.8, which is comparable to those of cuprates and iron-based high-Tc superconductors as well as infinite-layer nickelates. Above Tc, a well-defined pseudogap feature is manifested as a V-shaped dip in the differential conductance spanning an energy scale of 2Δg=0.95-3.0 meV. The pseudogap feature persists to the highest characteristic temperature of Tg=8-9 K and is gradually suppressed by magnetic field of Bg=9.0T regardless of its direction relative to the crystallographic axes. The observation of pseudogap features prior to the superconducting phase transition enriches the phase diagram of CeRh2As2 and provides a novel platform to study the interplay of unconventional superconductivity and pseudogap phenomena. △ Less

Submitted 4 January, 2025; originally announced January 2025.

Comments: 15 pages, 4 figures

Lorentz Transformation of the Energy Spectrum of the Equilibrium State of Massive Free Fields

Authors: Ruohan Xu, Tingzhang Shi, H. T. Quan

Abstract: In previous studies of relativistic thermodynamics, the temperature of a static system, as perceived by a moving observer, has traditionally been treated as a scalar. This assumption has also been extended to the research on the cosmic microwave background. However, the validity of this assumption is a consequence of the massless nature of photons. More generally, when an observer is in relative m… ▽ More In previous studies of relativistic thermodynamics, the temperature of a static system, as perceived by a moving observer, has traditionally been treated as a scalar. This assumption has also been extended to the research on the cosmic microwave background. However, the validity of this assumption is a consequence of the massless nature of photons. More generally, when an observer is in relative motion to a system, the thermal equilibrium state is characterized by a four-vector temperature. In this paper, we study the non-interacting massive Bosonic and Fermionic field systems. We derive the Lorentz transformation of the energy spectral density in the equilibrium state of these fields. In the massless limit for bosonic field, our results recover the transformation of black body radiation [G. W. Ford and R. F. O' Connell., Phys. Rev. E, 88, 044101(2013)], which corresponds to a scalar temperature with dipole anisotropy. For the massive fields, the moving equilibrium state cannot be characterized by a corresponding scalar temperature. This result shows the necessity of introducing four-vector temperature in relativistic thermodynamics. △ Less

Submitted 30 December, 2024; originally announced December 2024.

Simultaneous achievement of record-breaking colossal magnetoresistance and angular magnetoresistance in an antiferromagnetic semiconductor EuSe2

Authors: Qingxin Dong, Pengtao Yang, Zhihao Liu, Yuzhi Wang, Ziyi Liu, Tong Shi, Zhaoming Tian, Jianping Sun, Yoshiya Uwatoko, Quansheng Wu, Genfu Chen, Bosen Wang, Jinguang Cheng

Abstract: Magnetoresistance effect lays the foundation for spintronics, magnetic sensors and hard drives. The pursuit of magnetic materials with colossal magnetoresistance (CMR) and/or angular magnetoresistance (AMR) has attracted enduring research interest and extensive investigations over past decades. Here we report on the discovery of field-induced record-breaking CMR of ~ -10^14 % and AMR ~ 10^14% achi… ▽ More Magnetoresistance effect lays the foundation for spintronics, magnetic sensors and hard drives. The pursuit of magnetic materials with colossal magnetoresistance (CMR) and/or angular magnetoresistance (AMR) has attracted enduring research interest and extensive investigations over past decades. Here we report on the discovery of field-induced record-breaking CMR of ~ -10^14 % and AMR ~ 10^14% achieved simultaneously in an antiferromagnetic rare-earth dichalcogenide EuSe2. Such intriguing observations are attributed to strong magnetic anisotropy and magnetic-field induced antiferromagnetic to ferromagnetic transition of the localized Eu2+ spins, which in turn closes the bandgap by lifting the degeneracy of Se-5p bands near Fermi level. Our DFT calculations perfectly replicate the experimental findings based on the Brillouin function and carries transport model. The present work provides a potential simple antiferromagnetic material for achieving angle-sensitive spintronic devices. △ Less

Submitted 23 December, 2024; originally announced December 2024.

Comments: 17 pages, 4 figures

Boson-fermion universality of mesoscopic entanglement fluctuations in free systems

Authors: Cunzhong Lou, Chushun Tian, Zhixing Zou, Tao Shi, Lih-King Lim

Abstract: Entanglement fluctuations associated with Schrödinger evolution of wavefunctions offer a unique perspective on various fundamental issues ranging from quantum thermalization to state preparation in quantum devices. Very recently, a subset of present authors have shown that in a class of free-fermion lattice models and interacting spin chains, entanglement dynamics enters into a new regime at long… ▽ More Entanglement fluctuations associated with Schrödinger evolution of wavefunctions offer a unique perspective on various fundamental issues ranging from quantum thermalization to state preparation in quantum devices. Very recently, a subset of present authors have shown that in a class of free-fermion lattice models and interacting spin chains, entanglement dynamics enters into a new regime at long time, with entanglement probes displaying persistent temporal fluctuations, whose statistics falls into the seemingly disparate paradigm of mesoscopic fluctuations in condensed matter physics. This motivate us to revisit here entanglement dynamics of a canonical bosonic model in many-body physics, i.e., a coupled harmonic oscillator chain. We find that when the system is driven out of equilibrium, the long-time entanglement dynamics exhibits strictly the same statistical behaviors as that of free-fermion models. Specifically, irrespective of entanglement probes and microscopic parameters, the statistical distribution of entanglement fluctuations is flanked by asymmetric tails: sub-Gaussian for upward fluctuations and sub-Gamma for downward; moreover, the variance exhibits a crossover from the scaling $\sim 1/L$ to $\sim L_A^3/L^2$, as the subsystem size $L_A$ increases ($L$ the total system size). This insensitivity to the particle statistics, dubbed boson-fermion universality, is contrary to the common wisdom that statistical phenomena of many-body nature depend strongly on particle statistics. Together with our previous work, the present work indicates rich fluctuation phenomena in entanglement dynamics awaiting in-depth explorations. △ Less

Submitted 21 November, 2024; originally announced November 2024.

Comments: 18 pages, 7 figures

Variational approach to the dynamics of dissipative quantum impurity models

Authors: Yi-Fan Qu, Martino Stefanini, Tao Shi, Tilman Esslinger, Sarang Gopalakrishnan, Jamir Marino, Eugene Demler

Abstract: Recent experiments with quantum simulators using ultracold atoms and superconducting qubits have demonstrated the potential of controlled dissipation as a versatile tool for realizing correlated many-body states. However, determining the dynamics of dissipative quantum many-body systems remains a significant analytical and numerical challenge. In this work, we focus on a dissipative impurity probl… ▽ More Recent experiments with quantum simulators using ultracold atoms and superconducting qubits have demonstrated the potential of controlled dissipation as a versatile tool for realizing correlated many-body states. However, determining the dynamics of dissipative quantum many-body systems remains a significant analytical and numerical challenge. In this work, we focus on a dissipative impurity problem as a testbed for new methodological developments. We introduce an efficient non-perturbative framework that combines the superposition of Gaussian states (SGS) variational ansatz with the quantum trajectory approach to simulate open systems featuring a dissipative impurity. Applying this method to a spinful impurity subject to two-body losses and embedded in a bath of noninteracting fermions, we explore the full crossover from weak to strong dissipation regimes. The non-perturbative nature of the SGS ansatz allows us to thoroughly examine this crossover, providing comprehensive insights into the system's behavior. In the strong dissipation regime, our approach reproduces the finding that localized two-body losses can induce the Kondo effect [arXiv:2406.03527], characterized by a slowdown of spin relaxation and an enhancement of charge conductance. Furthermore, we reveal an exotic ``negative conductance" phenomenon at zero potential bias -- a counter-intuitive single-body effect resulting from intermediate dissipation and finite bandwidth. Finally, we investigate the formation of ferromagnetic domains and propose an extension to realize a higher-spin Kondo model using localized dissipation. △ Less

Submitted 3 July, 2025; v1 submitted 20 November, 2024; originally announced November 2024.

Comments: 19 pages, 7 figures. Close to published version. Editors' Suggestion

Journal ref: Phys. Rev. B 111, 155113 (2025)

Distinct many-body scars and emergent quantum phases driven by competing interactions in two-species Rydberg arrays

Authors: Lei-Yi-Nan Liu, Shun-Yao Yu, Shi-Rong Peng, Jie Sheng, Su Yi, Peng Xu, Shou-Shu Gong, Tao Shi, Jian Cui

Abstract: Rydberg atom arrays composed of multiple atomic species stand as a highly promising platform for quantum computation. However, the underlying physics of these systems as quantum many-body systems remains poorly understood, owing to the intricate competition between attractive and repulsive interactions, phenomena that entirely defy the Rydberg blockade mechanism. We systematically calculate the gr… ▽ More Rydberg atom arrays composed of multiple atomic species stand as a highly promising platform for quantum computation. However, the underlying physics of these systems as quantum many-body systems remains poorly understood, owing to the intricate competition between attractive and repulsive interactions, phenomena that entirely defy the Rydberg blockade mechanism. We systematically calculate the ground-state phase diagram of alternating two-species atom arrays and their quench dynamics. Our findings reveal several novel quantum states absent in traditional cold-atom platforms, such as the period-4 product state $|1100...\rangle$, the period-6 product state $|111000...\rangle$, and an order-disorder mixed phase. In the quench dynamics, we confirm $\mathbb{Z}_2$ ordered state qualify as novel quantum many-body scars. Based on our perturbation analysis, the underlying physics ought to be described by a series of Cooper pair states spanning the entire energy spectrum, rather than the PXP low-energy effective model. A detailed analysis is also provided regarding the experimental preparation of those product states. Numerical evidence demonstrates that the proposed scheme exhibits robustness against typical experimental imperfections, thereby confirming its experimental feasibility. Moreover, the ground-state problem of the two-species array naturally maps to more general combinatorial optimization problems, extending the class of optimization tasks accessible to programmable neutral-atom quantum processors. Our work paves a new way for quantum simulation of novel quantum many-body states, which emerge from the interplay between competing interactions among different atom species and quantum fluctuations. △ Less

Submitted 17 August, 2026; v1 submitted 28 August, 2024; originally announced August 2024.

Comments: 22 pages, 23 figures

Journal ref: Phys. Rev. B 114, 115406 (2026)

A topological Hund nodal line antiferromagnet

Authors: Xian P. Yang, Yueh-Ting Yao, Pengyu Zheng, Shuyue Guan, Huibin Zhou, Tyler A. Cochran, Che-Min Lin, Jia-Xin Yin, Xiaoting Zhou, Zi-Jia Cheng, Zhaohu Li, Tong Shi, Md Shafayat Hossain, Shengwei Chi, Ilya Belopolski, Yu-Xiao Jiang, Maksim Litskevich, Gang Xu, Zhaoming Tian, Arun Bansil, Zhiping Yin, Shuang Jia, Tay-Rong Chang, M. Zahid Hasan

Abstract: The interplay of topology, magnetism, and correlations gives rise to intriguing phases of matter. In this study, through state-of-the-art angle-resolved photoemission spectroscopy, density functional theory and dynamical mean-field theory calculations, we visualize a fourfold degenerate Dirac nodal line at the boundary of the bulk Brillouin zone in the antiferromagnet YMn2Ge2. We further demonstra… ▽ More The interplay of topology, magnetism, and correlations gives rise to intriguing phases of matter. In this study, through state-of-the-art angle-resolved photoemission spectroscopy, density functional theory and dynamical mean-field theory calculations, we visualize a fourfold degenerate Dirac nodal line at the boundary of the bulk Brillouin zone in the antiferromagnet YMn2Ge2. We further demonstrate that this gapless, antiferromagnetic Dirac nodal line is enforced by the combination of magnetism, space-time inversion symmetry and nonsymmorphic lattice symmetry. The corresponding drumhead surface states traverse the whole surface Brillouin zone. YMn2Ge2 thus serves as a platform to exhibit the interplay of multiple degenerate nodal physics and antiferromagnetism. Interestingly, the magnetic nodal line displays a d-orbital dependent renormalization along its trajectory in momentum space, thereby manifesting Hund coupling. Our findings offer insights into the effect of electronic correlations on magnetic Dirac nodal lines, leading to an antiferromagnetic Hund nodal line. △ Less

Submitted 15 August, 2024; originally announced August 2024.

Journal ref: Nature Communications volume 15, Article number: 7052 (2024)

Universal clusters in quasi-two-dimensional ultracold Fermi mixtures

Authors: Ruijin Liu, Tingting Shi, Matteo Zaccanti, Xiaoling Cui

Abstract: We study universal clusters in quasi-two dimensions (q2D) that consist of a light (L) atom interacting with two or three heavy (H) identical fermions, forming the trimer or tetramer bound state. The axial confinement in q2D is shown to lift the three-fold degeneracy of 3D trimer (tetramer) in $p$-wave channel and uniquely select the ground state with magnetic angular momentum $|m|=1$ ($m=0$). By v… ▽ More We study universal clusters in quasi-two dimensions (q2D) that consist of a light (L) atom interacting with two or three heavy (H) identical fermions, forming the trimer or tetramer bound state. The axial confinement in q2D is shown to lift the three-fold degeneracy of 3D trimer (tetramer) in $p$-wave channel and uniquely select the ground state with magnetic angular momentum $|m|=1$ ($m=0$). By varying the interaction or confinement strength, we explore the dimensional crossover of these clusters from 3D to 2D, characterized by a gradual change of critical H-L mass ratio for their emergence and momentum-space distribution. Importantly, we find that a finite effective range will {\it not} alter their critical mass ratios in the weak coupling regime. There, we establish an effective 2D model to quantitatively reproduce the properties of q2D clusters, and further identify the optimal interaction strengths for their detections in experiments. Our results suggest a promising prospect for observing universal clusters and associated high-order correlation effects in realistic q2D ultracold Fermi mixtures. △ Less

Submitted 5 October, 2024; v1 submitted 24 July, 2024; originally announced July 2024.

Comments: 6 pages, 4 figures, with supplementary material (8 pages, 4 figures)

Journal ref: Phys. Rev. Research 6, L042004 (2024)

Bose-Einstein condensates of microwave-shielded polar molecules

Authors: Wei-Jian Jin, Fulin Deng, Su Yi, Tao Shi

Abstract: We investigate the ground-state properties of the ultracold gases of bosonic microwave-shielded polar molecules. To account for the large shielding core of the inter-molecular potential, we adopt a variational ansatz incorporating the Jastrow correlation factor. We show that the system is always stable and supports a self-bound gas phase and an expanding gas phase. We also calculate the condensate… ▽ More We investigate the ground-state properties of the ultracold gases of bosonic microwave-shielded polar molecules. To account for the large shielding core of the inter-molecular potential, we adopt a variational ansatz incorporating the Jastrow correlation factor. We show that the system is always stable and supports a self-bound gas phase and an expanding gas phase. We also calculate the condensate fraction which is significantly reduced when the size of the shielding core of the two-body potential becomes comparable to the inter-molecular distance. Our studies distinguish the molecular condensates from the atomic ones and invalidate the application of the Gross-Pitaevskii equation to the microwave-shielded molecular gases. Our work paves the way for studying the Bose-Einstein condensations of ultracold gases of microwave-shielded polar molecules. △ Less

Submitted 10 June, 2024; originally announced June 2024.

Unveiling quantum phases in quasi-one-dimensional dipolar gases using continuous matrix product state

Authors: Li Peng, Junqiao Pan, Su Yi, Tao Shi

Abstract: We investigate the ground-state properties of the quasi-one-dimensional dipolar gases using continuous matrix product states techniques. Making use of the first- and second-order correlation functions, we find that the system supports the superfluid, super-Tonks-Girardeau, and quasicrystal phases according to the Luttinger liquid theory. We also map out the phase diagram on the parameter plane con… ▽ More We investigate the ground-state properties of the quasi-one-dimensional dipolar gases using continuous matrix product states techniques. Making use of the first- and second-order correlation functions, we find that the system supports the superfluid, super-Tonks-Girardeau, and quasicrystal phases according to the Luttinger liquid theory. We also map out the phase diagram on the parameter plane consisting the contact and dipolar interaction strengths. Furthermore, we compute the Luttinger parameter, the structure factor, and the momentum distribution of the system. Finally, we show that the predicted dipolar effect can potentially be observed in quasi-one-dimensional gases of polar molecules. △ Less

Submitted 26 May, 2024; originally announced May 2024.

Exact Work Distribution and Jarzynski's Equality of a Relativistic Particle in an Expanding Piston

Authors: Xianghang Zhang, Tingzhang Shi, H. T. Quan

Abstract: We study the non-equilibrium work in a pedagogical model of relativistic ideal gas. We obtain the exact work distribution and verify the Jarzynski's equality. In the non-relativistic limit, our results recover the non-relativistic results [arXiv:cond-mat/0502434]. We also find that, unlike the non-relativistic case, the work distribution no longer has zeros and the number of collisions in this rel… ▽ More We study the non-equilibrium work in a pedagogical model of relativistic ideal gas. We obtain the exact work distribution and verify the Jarzynski's equality. In the non-relativistic limit, our results recover the non-relativistic results [arXiv:cond-mat/0502434]. We also find that, unlike the non-relativistic case, the work distribution no longer has zeros and the number of collisions in this relativistic gas model is finite. In addition, based on an analysis of the experimental parameters, we conclude that it is difficult to detect the relativistic effects of the work distribution of the ideal gas in a piston system with the current experimental techniques. △ Less

Submitted 20 November, 2025; v1 submitted 23 March, 2024; originally announced March 2024.

Comments: Minor modifications. Version published on PRE

Journal ref: Phys. Rev. E 110, 024128 (2024)

AFSD-Physics: Exploring the governing equations of temperature evolution during additive friction stir deposition by a human-AI teaming approach

Authors: Tony Shi, Mason Ma, Jiajie Wu, Chase Post, Elijah Charles, Tony Schmitz

Abstract: This paper presents a modeling effort to explore the underlying physics of temperature evolution during additive friction stir deposition (AFSD) by a human-AI teaming approach. AFSD is an emerging solid-state additive manufacturing technology that deposits materials without melting. However, both process modeling and modeling of the AFSD tool are at an early stage. In this paper, a human-AI teamin… ▽ More This paper presents a modeling effort to explore the underlying physics of temperature evolution during additive friction stir deposition (AFSD) by a human-AI teaming approach. AFSD is an emerging solid-state additive manufacturing technology that deposits materials without melting. However, both process modeling and modeling of the AFSD tool are at an early stage. In this paper, a human-AI teaming approach is proposed to combine models based on first principles with AI. The resulting human-informed machine learning method, denoted as AFSD-Physics, can effectively learn the governing equations of temperature evolution at the tool and the build from in-process measurements. Experiments are designed and conducted to collect in-process measurements for the deposition of aluminum 7075 with a total of 30 layers. The acquired governing equations are physically interpretable models with low computational cost and high accuracy. Model predictions show good agreement with the measurements. Experimental validation with new process parameters demonstrates the model's generalizability and potential for use in tool temperature control and process optimization. △ Less

Submitted 29 January, 2024; originally announced January 2024.

Magnon Damping Minimum and Logarithmic Scaling in a Kondo-Heisenberg Model

Authors: Yuan Gao, Junsen Wang, Qiaoyi Li, Qing-Bo Yan, Tao Shi, Wei Li

Abstract: Recently, an anomalous temperature evolution of spin wave excitations has been observed in a van der Waals metallic ferromagnet Fe$_3$GeTe$_2$ (FGT) [S. Bao, et al., Phys. Rev. X 12, 011022 (2022)], whose theoretical understanding yet remains elusive. Here we study the spin dynamics of a ferromagnetic Kondo-Heisenberg lattice model at finite temperature, and propose a mechanism of magnon damping t… ▽ More Recently, an anomalous temperature evolution of spin wave excitations has been observed in a van der Waals metallic ferromagnet Fe$_3$GeTe$_2$ (FGT) [S. Bao, et al., Phys. Rev. X 12, 011022 (2022)], whose theoretical understanding yet remains elusive. Here we study the spin dynamics of a ferromagnetic Kondo-Heisenberg lattice model at finite temperature, and propose a mechanism of magnon damping that explains the intriguing experimental results. In particular, we find the magnon damping rate $γ(T)$ firstly decreases as temperature lowers, due to the reduced magnon-magnon scatterings. It then reaches a minimum at $T_{\rm d}^*$, and rises up again following a logarithmic scaling $γ(T) \sim \ln{(T_0/T)}$ (with $T_0$ a constant) for $T < T_{\rm d}^*$, which can be attributed to electron-magnon scatterings of spin-flip type. Moreover, we obtain the phase diagram containing the ferromagnetic and Kondo insulator phases by varying the Kondo coupling, which may be relevant for experiments on pressured FGT. The presence of a magnon damping minimum and logarithmic scaling at low temperature indicates the emergence of the Kondo effect reflected in the collective excitations of local moments in a Kondo lattice system. △ Less

Submitted 1 January, 2024; originally announced January 2024.

Effects of $p$-wave Interactions on Borromean Efimov Trimers in Heavy-Light Fermi Systems

Authors: Cai-Yun Zhao, Hui-Li Han, Ting-Yun Shi

Abstract: We investigate the effects of $p$-wave interactions on Efimov trimers in systems comprising two identical heavy fermions and a light particle, with mass ratios larger than $13.6$. Our focus lies on the borromean regime where the ground-state trimer exists in the absence of dimers. Using pair-wise Lennard-Jones potentials and concentrating on the $L^π = 1^{-}$ symmetry, we explore the critical valu… ▽ More We investigate the effects of $p$-wave interactions on Efimov trimers in systems comprising two identical heavy fermions and a light particle, with mass ratios larger than $13.6$. Our focus lies on the borromean regime where the ground-state trimer exists in the absence of dimers. Using pair-wise Lennard-Jones potentials and concentrating on the $L^π = 1^{-}$ symmetry, we explore the critical value of the interspecies $s$-wave scattering length $a_{c}$ at which the borromean state appears in several two-component particle systems. Our exploration encompasses the universal properties of $a_{c}$ and the influence of $p$-wave fermion-fermion interactions on its value. We find that, in the absence of $p$-wave fermion-fermion interactions, $a_{c}$ is determined universally by the van der Waals radius and mass ratio. However, the introduction of $p$-wave fermion-fermion interactions unveiled a departure from this universality. Our calculations show that the critical interspecies scattering length $a_{c}$ now depends on the details of the fermion-fermion $p$-wave interaction. And, the presence of $p$-wave fermion-fermion interactions favors the formation of the borromean state. Additionally, our investigation reveals that Efimov effect in the $1^{-}$ symmetry persist even when the fermion-fermion interaction reaches the $p$-wave unitary limit. △ Less

Submitted 10 March, 2025; v1 submitted 24 July, 2023; originally announced July 2023.

Comments: 17 pages,10 figures

Light-Driven Nanoscale Vectorial Currents

Authors: Jacob Pettine, Prashant Padmanabhan, Teng Shi, Lauren Gingras, Luke McClintock, Chun-Chieh Chang, Kevin W. C. Kwock, Long Yuan, Yue Huang, John Nogan, Jon K. Baldwin, Peter Adel, Ronald Holzwarth, Abul K. Azad, Filip Ronning, Antoinette J. Taylor, Rohit P. Prasankumar, Shi-Zeng Lin, Hou-Tong Chen

Abstract: Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. How… ▽ More Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometer spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science. Here, we introduce vectorial optoelectronic metasurfaces in which ultrafast light pulses induce local directional charge flows around symmetry-broken plasmonic nanostructures, with tunable responses and arbitrary patterning down to sub-diffractive nanometer scales. Local symmetries and vectorial current distributions are revealed by polarization- and wavelength-sensitive electrical readout and terahertz (THz) emission, while spatially-tailored global currents are demonstrated in the direct generation of elusive broadband THz vector beams. We show that in graphene, a detailed interplay between electrodynamic, thermodynamic, and hydrodynamic degrees of freedom gives rise to rapidly-evolving nanoscale driving forces and charge flows under extreme temporal and spatial confinement. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, THz spectroscopies, nano-magnetism, and ultrafast information processing. △ Less

Submitted 21 October, 2023; v1 submitted 21 July, 2023; originally announced July 2023.

Journal ref: Nature 626, 984-989 (2024)

Ultracold field-linked tetratomic molecules

Authors: Xing-Yan Chen, Shrestha Biswas, Sebastian Eppelt, Andreas Schindewolf, Fulin Deng, Tao Shi, Su Yi, Timon A. Hilker, Immanuel Bloch, Xin-Yu Luo

Abstract: Ultracold polyatomic molecules offer intriguing new opportunities in cold chemistry, precision measurements, and quantum information processing, thanks to their rich internal structure. However, their increased complexity compared to diatomic molecules presents a formidable challenge to employ conventional cooling techniques. Here, we demonstrate a new approach to create ultracold polyatomic molec… ▽ More Ultracold polyatomic molecules offer intriguing new opportunities in cold chemistry, precision measurements, and quantum information processing, thanks to their rich internal structure. However, their increased complexity compared to diatomic molecules presents a formidable challenge to employ conventional cooling techniques. Here, we demonstrate a new approach to create ultracold polyatomic molecules by electroassociation in a degenerate Fermi gas of microwave-dressed polar molecules through a field-linked resonance. Starting from ground state NaK molecules, we create around $1.1\times 10^3$ tetratomic (NaK)$_2$ molecules, with a phase space density of $0.040(3)$ at a temperature of $134(3)\,\text{nK}$, more than $3000$ times colder than previously realized tetratomic molecules. We observe a maximum tetramer lifetime of $8(2)\,\text{ms}$ in free space without a notable change in the presence of an optical dipole trap, indicating these tetramers are collisionally stable. The measured binding energy and lifetime agree well with parameter-free calculations, which outlines pathways to further increase the lifetime of the tetramers. Moreover, we directly image the dissociated tetramers through microwave-field modulation to probe the anisotropy of their wave function in momentum space. Our result demonstrates a universal tool for assembling ultracold polyatomic molecules from smaller polar molecules, which is a crucial step towards Bose--Einstein condensation (BEC) of polyatomic molecules and towards a new crossover from a dipolar Bardeen-Cooper-Schrieffer (BCS) superfluid to a BEC of tetramers. Additionally, the long-lived FL state provides an ideal starting point for deterministic optical transfer to deeply bound tetramer states. △ Less

Submitted 1 June, 2023; originally announced June 2023.

Journal ref: Nature 626, 283 (2024)

Microwave shielding of bosonic NaRb molecules

Authors: Junyu Lin, Guanghua Chen, Mucan Jin, Zhaopeng Shi, Fulin Deng, Wenxian Zhang, Goulven Quéméner, Tao Shi, Su Yi, Dajun Wang

Abstract: Recent years have witnessed tremendous progresses in creating and manipulating ground-state ultracold polar molecules. However, the two-body loss regardless of the chemical reactivities is still a hurdle for many future explorations. Here, we investigate the loss suppression of non-reactive bosonic $^{23}$Na$^{87}$Rb molecules with a circular polarized microwave blue-detuned to the rotational tran… ▽ More Recent years have witnessed tremendous progresses in creating and manipulating ground-state ultracold polar molecules. However, the two-body loss regardless of the chemical reactivities is still a hurdle for many future explorations. Here, we investigate the loss suppression of non-reactive bosonic $^{23}$Na$^{87}$Rb molecules with a circular polarized microwave blue-detuned to the rotational transition. We achieve suppression of the loss by two orders of magnitude with the lowest two-body loss rate coefficient reduced to $3\times10^{-12}~\rm{cm^3/s}$. Meanwhile, the elastic collision rate coefficient is increased to the $10^{-8}~\rm{cm^3/s}$ level. The large good-to-bad collision ratio has allowed us to carry out evaporative cooling of $^{23}$Na$^{87}$Rb with an efficiency of 1.7(2), increasing the phase-space density by a factor of 10. With further improvements, this technique holds great promises for creating a Bose-Einstein condensate of ultracold polar molecules. △ Less

Submitted 30 April, 2023; v1 submitted 17 April, 2023; originally announced April 2023.

Comments: 11 pages, 8 figures. Figure 3(c) is updated based on the calculation in Appendix D2. The 1st version was submitted on 17 Apr 2023

Journal ref: Phys. Rev. X 13, 031032 (2023)

Tighter upper bounds on the critical temperature of two-dimensional superconductors and superfluids from the BCS to the Bose regime

Authors: Tingting Shi, Wei Zhang, C. A. R. Sá de Melo

Abstract: We discuss standard and tighter upper bounds on the critical temperature $T_c$ of two-dimensional (2D) superconductors and superfluids versus particle density $n$ or filling factor $ν$ for continuum and lattice systems from the Bardeen-Cooper-Schrieffer (BCS) to Bose regime. We discuss only one-band Hamiltonians, where the transition from the normal to superconducting (superfluid) phase is governe… ▽ More We discuss standard and tighter upper bounds on the critical temperature $T_c$ of two-dimensional (2D) superconductors and superfluids versus particle density $n$ or filling factor $ν$ for continuum and lattice systems from the Bardeen-Cooper-Schrieffer (BCS) to Bose regime. We discuss only one-band Hamiltonians, where the transition from the normal to superconducting (superfluid) phase is governed by Berezinskii-Kosterlitz-Thouless (BKT) mechanism of vortex-antivortex binding, such that a direct relation between the superfluid density tensor and $T_c$ exists. We demonstrate that it is imperative to consider at least the full effect of phase fluctuations of order parameter for superconductivity (superfluidity) to establish tighter bounds. Using the renormalization group, we obtain phase-fluctuation critical temperature $T_c^θ$, a much tighter upper bound to critical temperature supremum $T_c^{\rm sup}$ than standard critical temperature upper bound $T_c^{\rm up1}$ from Ferrell-Glover-Tinkham sum rule. We go beyond textbook phase-fluctuation theories and show that chemical potential renormalization, order parameter equation, and Nelson-Kosterlitz relation need to be solved self-consistently and simultaneously with renormalization group flow equation to produce $T_c^θ$ over the entire BCS-Bose crossover. We note that an analytic theory including modulus fluctuations of the order parameter valid throughout the BCS-Bose evolution is still lacking, but the inclusion of modulus fluctuations can only produce a critical temperature lower than $T_c^θ$ and thus produce an even tighter bound to $T_c^{\rm sup}$. We conclude by indicating that if the measured critical temperature exceeds $T_c^θ$ in experiments involving 2D single-band systems, then a non-BKT mechanism must be invoked to describe the superconducting (superfluid) transition. △ Less

Submitted 20 March, 2023; originally announced March 2023.

Comments: 12 pages, 5 figures, a long version of the short paper listed on arXiv:2203.05478