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Universal Short-Imaginary-Time Quantum Critical Dynamics Near Boundaries
Authors:
Yu-Rong Shu,
Yuan-Biao Li,
Shuai Yin
Abstract:
While imaginary-time evolution has long served as a standard paradigm for ground-state preparation in numerical simulations and quantum devices, its intrinsic dynamical properties has been largely overlooked. Here, we investigate the short-imaginary-time critical dynamics in quantum systems with boundaries. A universal scaling theory is developed and verified in the two-dimensional quantum Ising m…
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While imaginary-time evolution has long served as a standard paradigm for ground-state preparation in numerical simulations and quantum devices, its intrinsic dynamical properties has been largely overlooked. Here, we investigate the short-imaginary-time critical dynamics in quantum systems with boundaries. A universal scaling theory is developed and verified in the two-dimensional quantum Ising model, uncovering rich dynamic critical behaviors dictated by boundary universality classes. For ordered initial states, the boundary order parameter $M_s$ decays with imaginary time $τ$ as $M_s \propto τ^{-β_1/νz}$, where $β_1$ denotes the boundary order parameter exponent, and $ν$ and $z$ correspond to the correlation length exponent and the dynamic exponent, respectively. For disordered initial states, the autocorrelation of the boundary order parameter is governed by a novel critical exponent $θ_1$, which is closely related to the critical initial slip behavior of $M_s$ characterized by the corresponding exponent $θ_1'$. In contrast to its positive bulk counterpart, the boundary initial-slip exponent $θ_1'$ is negative for the ordinary transition while remaining positive for the special transition. Although the static universality classes of $d$-dimensional quantum phase transitions generally coincide with those of $(d+1)$-dimensional classical phase transitions, we show that $θ_1$ does not follow this conventional quantum-classical mapping. We further discuss the implications of our results for more exotic forms of boundary criticality. Our findings provide new physical insights into boundary critical dynamics and offer a novel route for probing exotic boundary critical behaviors in quantum many-body systems.
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Submitted 1 July, 2026;
originally announced July 2026.
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Coexistence of High Temperature Superconductivity and Antiferromagnetic Order in a Cuprate with Multiple Hole Fermi Pockets
Authors:
Xiangyu Luo,
Yinghao Li,
Hao Chen,
Yiwen Chen,
Jumin Shi,
Taimin Miao,
Bo Liang,
Wenpei Zhu,
Neng Cai,
Xiaolin Ren,
Yingjie Shu,
Chaohui Yin,
Jiuxiang Zhang,
Chengtian Lin,
Shenjin Zhang,
Zhimin Wang,
Fengfeng Zhang,
Feng Yang,
Qinjun Peng,
Zuyan Xu,
Guodong Liu,
Xintong Li,
Hanqing Mao,
Tao Xiang,
Lin Zhao
, et al. (1 additional authors not shown)
Abstract:
The intricate relationship between high temperature superconductivity and antiferromagnetic order in cuprates, and the fundamental origin of electron pairing remain open questions. By utilizing high-resolution laser-based spatially-resolved angle-resolved photoemission spectroscopy, we investigate the seven-layer $Bi_{2}Sr_{2}Ca_{6}Cu_{7}O_{18+δ}$ (Bi2267) and identify a cuprate system that consis…
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The intricate relationship between high temperature superconductivity and antiferromagnetic order in cuprates, and the fundamental origin of electron pairing remain open questions. By utilizing high-resolution laser-based spatially-resolved angle-resolved photoemission spectroscopy, we investigate the seven-layer $Bi_{2}Sr_{2}Ca_{6}Cu_{7}O_{18+δ}$ (Bi2267) and identify a cuprate system that consists of multiple hole Fermi pockets. The observed Fermi pockets exhibit pronounced momentum-, temperature- and Fermi surface-dependent energy gaps. Crucially, high temperature superconductivity with a critical temperature ($T_{\mathrm{c}}$) of $\sim$75 K emerges in a system with multiple Fermi pockets and the presence of strong antiferromagnetic order and correlations. In particular, substantial electron pairing is observed along the Fermi pocket with an energy gap up to $\sim$42 meV in lightly-doped CuO$_{2}$ planes ($p\sim$0.05). These findings challenge the conventional understanding of the roles of the nodal and antinodal electronic states in driving high-temperature superconductivity. They show that superconductivity and antiferromagnetism can coexist in a cuprate with multiple Fermi pockets, offering further insights into the pairing mechanism in cuprate superconductors.
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Submitted 7 June, 2026;
originally announced June 2026.
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Persistent Fermi Pockets and Robust Electron Pairing in Lightly Doped CuO$_2$ Planes of Cuprate Superconductors
Authors:
Hao Chen,
Jumin Shi,
Yinghao Li,
Xiangyu Luo,
Yiwen Chen,
Chaohui Yin,
Yingjie Shu,
Jiuxiang Zhang,
Taimin Miao,
Bo Liang,
Wenpei Zhu,
Neng Cai,
Xiaolin Ren,
Chengtian Lin,
Shenjin Zhang,
Zhimin Wang,
Fengfeng Zhang,
Feng Yang,
Qinjun Peng,
Zuyan Xu,
Guodong Liu,
Hanqing Mao,
Xintong Li,
Tao Xiang,
Lin Zhao
, et al. (1 additional authors not shown)
Abstract:
High temperature superconductivity in cuprate superconductors is generally considered to be generated from doping the Mott insulators. The fundamental nature of the doped parent compounds as well as the microscopic origin of electron pairing remain critical issues in understanding the emergence of superconductivity. Here, using high-resolution spatially-resolved laser angle-resolved photoemission…
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High temperature superconductivity in cuprate superconductors is generally considered to be generated from doping the Mott insulators. The fundamental nature of the doped parent compounds as well as the microscopic origin of electron pairing remain critical issues in understanding the emergence of superconductivity. Here, using high-resolution spatially-resolved laser angle-resolved photoemission spectroscopy, we investigate the intrinsic electronic structures of the CuO$_2$ planes in multilayer cuprates Bi$_2$Sr$_2$Ca$_{n-1}$Cu$_n$O$_{2n+4+δ}$ (n=5$\sim$8). The inner CuO$_2$ planes are well shielded from the disorders and provide a rare and ideal platform to probe the intrinsic electronic phase diagram. We observe well-defined Fermi pockets with hole doping levels as low as 0.007, demonstrating an abrupt transition from the parent Mott insulator to a metallic state upon the introduction of an infinitesimal amount of doping. The innermost CuO$_2$ planes (IP$_0$) display gapless Fermi pockets, while the second innermost planes (IP$_1$) exhibit anisotropic superconducting gaps up to $\sim$33$\,$meV, indicative of robust electron pairing coexisting with strong antiferromagnetic order. Our findings provide a revised framework for understanding the doping-driven transitions and pairing mechanisms in cuprate superconductors.
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Submitted 25 April, 2026;
originally announced April 2026.
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Unusual Dual Flat Bands and two-dimensional Dirac-node Arc State in Kagome Metal Ni3In2S2
Authors:
Bo Liang,
Yichen Liu,
Jie Pang,
Hanbin Deng,
Taimin Miao,
Wenpei Zhu,
Neng Cai,
Tiantian Zhang,
Jiayu Liu,
Zhicheng Jiang,
Zhanfeng Liu,
Hongen Zhu,
Yuliang Li,
Tongrui Li,
Mingkai Xu,
Hao Chen,
Xiaolin Ren,
Chaohui Yin,
Yingjie Shu,
Yiwen Chen,
Yu-Tian Zhang,
Zhengtai Liu,
Dawei Shen,
Mao Ye,
Fengfeng Zhang
, et al. (14 additional authors not shown)
Abstract:
Kagome materials are at the frontier of condensed matter physics. An ideal kagome lattice features only one geometrically frustrated flat band spanning the entire momentum space and a single Dirac cone at the Brillouin-zone corners. However, for the first time, here we observe unusual flat-band and Dirac physics in the newly discovered "322" kagome material Ni3In2S2 by combining high-resolution sy…
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Kagome materials are at the frontier of condensed matter physics. An ideal kagome lattice features only one geometrically frustrated flat band spanning the entire momentum space and a single Dirac cone at the Brillouin-zone corners. However, for the first time, here we observe unusual flat-band and Dirac physics in the newly discovered "322" kagome material Ni3In2S2 by combining high-resolution synchrotron- and laser-based angle-resolved photoemission spectroscopy with a micro-focused beam, scanning tunneling microscopy, and first-principles calculations. We resolve two distinct electronic flat-band states located in close proximity to the Fermi level: a robust Topological Surface Flat Band at ~40 meV below the Fermi level on the Sulfur-terminated surface, originating from weak topological insulator states, and a kagome lattice-derived flat band at ~100 meV binding energy with an ultranarrow bandwidth (~5 meV). Instead of the single Dirac cone, the Indium-terminated surface hosts a rare two-dimensional Dirac-node arc state, where the gapless Dirac nodes extend along an open one-dimensional line crossing the Brillouin-zone boundary, exhibiting sharp linear dispersion, exceptionally high Fermi velocity, and pronounced circular dichroism. These findings establish Ni3In2S2 as a unique topological kagome metal in which multiple flat-band states of different physical origin coexist with an unusual Dirac-node arc, opening an avenue for discovering flat-band--driven and topology-enabled quantum phenomena.
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Submitted 26 January, 2026;
originally announced January 2026.
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Realization of staircase topological Anderson phase transitions
Authors:
Marwa Mannai,
Yaoyao Shu,
Sonia Haddad,
Mina Ren,
Hong Chen,
Yong Sun,
Hisham Sati
Abstract:
One-dimensional topological Anderson insulators provide a paradigm for disorder-induced topological phases in which the underlying system turns from a trivial to a topological phase. It is widely recognized that the latter vanishes at large disorder amplitude. Here, and contrary to the general belief, we provide evidence for a successive disorder-driven topological transitions in a single-wall nan…
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One-dimensional topological Anderson insulators provide a paradigm for disorder-induced topological phases in which the underlying system turns from a trivial to a topological phase. It is widely recognized that the latter vanishes at large disorder amplitude. Here, and contrary to the general belief, we provide evidence for a successive disorder-driven topological transitions in a single-wall nanotube, culminating in a topological Anderson phase that remains unexpectedly robust at strong disorder. This phenomenon is confirmed by analysis of the corresponding topological invariant, which increases stepwise as disorder increases, giving evidence for the emergence of edge states. We experimentally implement these topological Anderson staircase phase transitions in a one-dimensional topolectrical circuit, where the persistence of edge states is revealed by node-voltage measurements. The robustness of the edge states is corroborated by numerical calculations of their localization properties. Our work opens the road to topological disordertronics, where topological phases can be tuned by disorder.
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Submitted 21 January, 2026;
originally announced January 2026.
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Universal Driven Critical Dynamics near the Boundary
Authors:
Yu-Rong Shu,
Shuai Yin
Abstract:
The celebrated Kibble-Zurek mechanism (KZM) describes the scaling of physical quantities when external parameters sweep through a critical point. Boundaries are ubiquitous in real systems, and critical behaviors near the boundary have attracted extensive research. Different boundary universality classes, including ordinary, special, extraordinary, and surface transitions, have been identified. How…
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The celebrated Kibble-Zurek mechanism (KZM) describes the scaling of physical quantities when external parameters sweep through a critical point. Boundaries are ubiquitous in real systems, and critical behaviors near the boundary have attracted extensive research. Different boundary universality classes, including ordinary, special, extraordinary, and surface transitions, have been identified. However, the driven critical dynamics near boundaries remains unexplored. Here, we systematically investigate the driven critical dynamics in various boundary universality classes of the Ising model in both two and three dimensions, and discover a wealth of dynamic scaling behaviors. We find that for heating dynamics in all boundary universality classes, as well as for cooling dynamics in special, extraordinary, and surface transitions, the dynamic scaling behaviors of the order parameter can be described by a normal generalization of the KZM, called boundary finite-time scaling (BFTS). In contrast, for cooling dynamics in ordinary transition, we discover an abnormal logarithmic scaling on the driving rate. Moreover, for the special transition, in addition to temperature driving, we also consider the driven dynamics by driving the surface couplings. For increasing the surface coupling across the special transition point along the line of the ordinary transition, the prerequisite of the KZM, which requires that the correlation length/time in the initial state to be short-ranged, breaks down. We develop a generalized BFTS for a nonequilibrium initial state characterized by the waiting time, or the ``age'', of the boundary. Possible generalizations are also discussed.
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Submitted 12 September, 2025;
originally announced September 2025.
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Doping Evolution of Nodal Electron Dynamics in Trilayer Cuprate Superconductor Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+δ}$ Revealed by Laser-Based Angle-Resolved Photoemission Spectroscopy
Authors:
Hao Chen,
Jumin Shi,
Xiangyu Luo,
Yinghao Li,
Yiwen Chen,
Chaohui Yin,
Yingjie Shu,
Jiuxiang Zhang,
Taimin Miao,
Bo Liang,
Wenpei Zhu,
Neng Cai,
Xiaolin Ren,
Chengtian Lin,
Shenjin Zhang,
Zhimin Wang,
Fengfeng Zhang,
Feng Yang,
Qinjun Peng,
Zuyan Xu,
Guodong Liu,
Hanqing Mao,
Xintong Li,
Lin Zhao,
X. J. Zhou
Abstract:
The doping evolution of the nodal electron dynamics in the trilayer cuprate superconductor Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+δ}$ (Bi2223) is investigated using high-resolution laser-based angle-resolved photoemission spectroscopy (ARPES). Bi2223 single crystals with different doping levels are prepared by controlled annealing which cover the underdoped, optimally-doped and overdoped regions. The elec…
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The doping evolution of the nodal electron dynamics in the trilayer cuprate superconductor Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+δ}$ (Bi2223) is investigated using high-resolution laser-based angle-resolved photoemission spectroscopy (ARPES). Bi2223 single crystals with different doping levels are prepared by controlled annealing which cover the underdoped, optimally-doped and overdoped regions. The electronic phase diagram of Bi2223 is established which describes the T$_\mathrm{c}$ dependence on the sample doping level. The doping dependence of the nodal Fermi momentum for the outer (OP) and inner (IP) CuO$_2$ planes is determined. Charge distribution imbalance between the OP and IP CuO$_2$ planes is quantified, showing enhanced disparity with increasing doping. Nodal band dispersions demonstrate a prominent kink at $\sim$94$\,$meV in the IP band, attributed to the unique Cu coordination in the IP plane, while a weaker $\sim$60$\,$meV kink is observed in the OP band. The nodal Fermi velocity of both OP and IP bands is nearly constant at $\sim$1.62$\,$eVÅ independent of doping. These results provide important information to understand the origin of high T$_\mathrm{c}$ and superconductivity mechanism in high temperature cuprate superconductors.
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Submitted 13 August, 2025;
originally announced August 2025.
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Neutron Spin Resonance Near a Lifshitz Transition in Overdoped Ba$_{0.4}$K$_{0.6}$Fe$_2$As$_2$
Authors:
Yang Li,
Dingsong Wu,
Yingjie Shu,
Bo Liu,
Uwe Stuhr,
Guochu Deng,
Anton P. J. Stamp,
Lin Zhao,
Xingjiang Zhou,
Shiliang Li,
Amit Pokhriyal,
Haranath Ghosh,
Wenshan Hong,
Huiqian Luo
Abstract:
Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors (FeSCs). Here, we report inelastic neutron scattering results on the hole overdoped Ba$_{0.4}$K$_{0.6}$Fe$_2$As$_2$ near a Lifshitz transition, where the electron pocket at $M$ point is nearly replace by four hole pockets. In the normal state, the spi…
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Elucidating the relationship between spin excitations and fermiology is essential for clarifying the pairing mechanism in iron-based superconductors (FeSCs). Here, we report inelastic neutron scattering results on the hole overdoped Ba$_{0.4}$K$_{0.6}$Fe$_2$As$_2$ near a Lifshitz transition, where the electron pocket at $M$ point is nearly replace by four hole pockets. In the normal state, the spin excitations are observed at incommensurate wave vectors with chimney-like dispersions. By cooling down to the superconducting state, a neutron spin resonance mode emerges with a peak energy of $E_r=$ 14-15 meV weakly modulated along $L$-direction. The incommensurability notably increases at low energies, giving rise to downward dispersions of the resonance mode. This behavior contrasts sharply with the upward dispersions of resonance observed in optimally doped Ba$_{0.67}$K$_{0.33}$Fe$_2$As$_2$ contributed by the hole to electron scattering, but resembles with the cases in KFe$_2$As$_2$ and KCa$_2$Fe$_4$As$_4$F$_2$ where the fermiology are dominated by hole pockets. These results highlight the critical role of electronic structure modifications near the Fermi level, especially in governing interband scattering under imperfect nesting conditions, which fundamentally shape the spin dynamics of FeSCs.
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Submitted 16 May, 2025;
originally announced May 2025.
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Finite-time scaling with two characteristic time scales: Driven critical dynamics with emergent symmetry
Authors:
Yu-Rong Shu,
Li-Ying Yang,
Shuai Yin
Abstract:
Critical points with emergent symmetry exhibit intriguing scaling properties induced by two divergent length scales, attracting extensive investigations recently. We study the driven critical dynamics in a three-dimensional $q$-state clock model, in which the ordered phase breaks the $Z_q$ discrete symmetry, while an emergent $U(1)$ symmetry appears at the critical point. By increasing the tempera…
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Critical points with emergent symmetry exhibit intriguing scaling properties induced by two divergent length scales, attracting extensive investigations recently. We study the driven critical dynamics in a three-dimensional $q$-state clock model, in which the ordered phase breaks the $Z_q$ discrete symmetry, while an emergent $U(1)$ symmetry appears at the critical point. By increasing the temperature at a finite velocity $v$ to traverse the critical point from the ordered phase, we uncover rich dynamic scaling properties beyond the celebrated Kibble-Zurek mechanism. Our findings reveal the existence of two finite-time scaling (FTS) regions, characterized by two driving-induced time scales $ζ_d\propto v^{-z/r}$ and $ζ_d'\propto v^{-z/r'}$, respectively. Here $z$ is the dynamic exponent, $r$ is the usual critical exponent of $v$, and $r'$ represents an additional critical exponent of $v$ associated with the dangerously irrelevant scaling variable. While the square of the order parameter $M^2$ obeys the usual FTS form, the angular order parameter $φ_q$ shows remarkably distinct scaling behaviors controlled by both FTS regions. For small $v$, $φ_q$ is dominated by the time scale $ζ_d$, whereas for large $v$, $φ_q$ is governed by the second time scale $ζ_d'$. We verify the universality of these scaling properties in models with both isotropic and anisotropic couplings. Our theoretical insights provide a promising foundation for further experimental investigations in the hexagonal RMnO$_3$ (R=rare earth) materials.
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Submitted 20 March, 2025;
originally announced March 2025.
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High-Velocity Magnetic Domain Wall Motion Driven by Acoustic Spin Transfer Torque
Authors:
Jiacheng Lu,
Fa Chen,
Yiming Shu,
Yukang Wen,
Hang Zou,
Yuhao Liu,
Shiheng Liang,
Wei Luo,
Yue Zhang
Abstract:
We predict high-velocity magnetic domain wall (DW) motion driven by out-of-plane acoustic spin in surface acoustic waves (SAWs). We demonstrate that the SAW propagating at a 30-degree angle relative to the x-axis of a 128-degree Y-LiNbO3 substrate exhibits uniform out-of-plane spin angular momentum. This acoustic spin triggers the DW motion at a velocity exceeding 50 m/s in a way that is similar t…
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We predict high-velocity magnetic domain wall (DW) motion driven by out-of-plane acoustic spin in surface acoustic waves (SAWs). We demonstrate that the SAW propagating at a 30-degree angle relative to the x-axis of a 128-degree Y-LiNbO3 substrate exhibits uniform out-of-plane spin angular momentum. This acoustic spin triggers the DW motion at a velocity exceeding 50 m/s in a way that is similar to the spin-transfer-torque (STT) effect. This phenomenon highlights the potential of acoustic spin in enabling rapid DW displacement, offering an innovative approach to developing energy-efficient spintronic devices.
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Submitted 14 April, 2025; v1 submitted 25 February, 2025;
originally announced February 2025.
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Scaling corrections in driven critical dynamics: Application to a two-dimensional dimerized quantum Heisenberg model
Authors:
Jing-Wen Liu,
Shuai Yin,
Yu-Rong Shu
Abstract:
Driven critical dynamics in quantum phase transitions holds significant theoretical importance, and also practical applications in fast-developing quantum devices. While scaling corrections have been shown to play important roles in fully characterizing equilibrium quantum criticality, their impact on nonequilibrium critical dynamics has not been extensively explored. In this work, we investigate…
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Driven critical dynamics in quantum phase transitions holds significant theoretical importance, and also practical applications in fast-developing quantum devices. While scaling corrections have been shown to play important roles in fully characterizing equilibrium quantum criticality, their impact on nonequilibrium critical dynamics has not been extensively explored. In this work, we investigate the driven critical dynamics in a two-dimensional quantum Heisenberg model. We find that in this model the scaling corrections arising from both finite system size and finite driving rate must be incorporated into the finite-time scaling form in order to properly describe the nonequilibrium scaling behaviors. In addition, improved scaling relations are obtained from the expansion of the full scaling form. We numerically verify these scaling forms and improved scaling relations for different starting states using the nonequilibrium quantum Monte Carlo algorithm.
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Submitted 7 February, 2025;
originally announced February 2025.
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Anomalous Magnetotransport in the Paramagnetic State of a Magnetic Kagome Metal EuTi$_3$Bi$_4$
Authors:
Yun Shu,
Xinrun Mi,
Yuhao Wei,
Sixue Tao,
Aifeng Wang,
Yisheng Chai,
Dashuai Ma,
Xiaolong Yang,
Mingquan He
Abstract:
We investigate the electrical transport properties of a magnetic kagome metal EuTi$_3$Bi$_4$, which undergoes magnetic ordering below $T_\mathrm{c}=10.5$ K. Unlike typical magnets showing anomalous magnetotransport in their ordered states, EuTi$_3$Bi$_4$ exhibits unusual magnetotransport behaviors in its paramagnetic phase. Specifically, the magnetoconductivity shows a linear dependence on magneti…
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We investigate the electrical transport properties of a magnetic kagome metal EuTi$_3$Bi$_4$, which undergoes magnetic ordering below $T_\mathrm{c}=10.5$ K. Unlike typical magnets showing anomalous magnetotransport in their ordered states, EuTi$_3$Bi$_4$ exhibits unusual magnetotransport behaviors in its paramagnetic phase. Specifically, the magnetoconductivity shows a linear dependence on magnetic field at low fields below $\sim 1$ T, and the Hall conductivity undergoes a sign change below about 2 T. These behaviors resemble those observed in the charge density wave (CDW) phase of kagome metals $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs). The anomalous magnetotransport in $A$V$_3$Sb$_5$ has commonly been attributed to the possible emergence of a time-reversal symmetry breaking chiral CDW order. However, given the absence of CDW in EuTi$_3$Bi$_4$ and its manifestation exclusively in the paramagnetic state, the anomalous magnetotransport observed in EuTi$_3$Bi$_4$ is likely associated with multiband transport and/or the van Hove singularities near the Fermi level.
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Submitted 6 January, 2025; v1 submitted 5 January, 2025;
originally announced January 2025.
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Modeling and Measurement of Lead Tip Heating in Implanted Wires with Loops
Authors:
Lydia J Bardwell Speltz,
Seung-Kyun Lee,
Yunhong Shu,
Matt A Bernstein
Abstract:
Purpose: To theoretically and experimentally study implant lead tip heating caused by radiofrequency (RF) power deposition in different wire configurations that contain loop(s). Methods: Maximum temperature rise caused by RF heating was measured at 1.5T on 20 insulated, capped wires with various loop and straight segment configurations. The experimental results were compared with predictions from…
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Purpose: To theoretically and experimentally study implant lead tip heating caused by radiofrequency (RF) power deposition in different wire configurations that contain loop(s). Methods: Maximum temperature rise caused by RF heating was measured at 1.5T on 20 insulated, capped wires with various loop and straight segment configurations. The experimental results were compared with predictions from the previously reported simple exponential and the adapted transmission line models, as well as with a long-wavelength approximation. Results: Both models effectively predicted the trends in lead tip temperature rise for all the wire configurations, with the adapted transmission line model showing superior accuracy. For superior/inferior (S/I)-oriented wires, increasing the number of loops decreased the overall heating. However, when wires were oriented right/left (R/L) where the x-component of the electric field is negligible, additional loops increased the overall heating. Conclusion: The simple exponential and the adapted transmission line models previously developed for, and tested on, straight wires require no additional terms or further modification to account for RF heating in a variety of loop configurations. These results extend the usefulness of the models to manage implanted device lead tip heating and provide theoretical insight regarding the role of loops and electrical lengths in managing RF safety of implanted devices.
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Submitted 19 December, 2024;
originally announced December 2024.
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Absence of BCS-BEC Crossover in FeSe0.45Te0 55 Superconductor
Authors:
Junjie Jia,
Yadong Gu,
Chaohui Yin,
Yingjie Shu,
Yiwen Chen,
Jumin Shi,
Xing Zhang,
Hao Chen,
Taimin Miao,
Xiaolin Ren,
Bo Liang,
Wenpei Zhu,
Neng Cai,
Fengfeng Zhang,
Shenjin Zhang,
Feng Yang,
Zhimin Wang,
Qinjun Peng,
Zuyan Xu,
Hanqing Mao,
Guodong Liu,
Zhian Ren,
Lin Zhao,
X. J. Zhou
Abstract:
In iron-based superconductor Fe(Se,Te), a flat band-like feature near the Fermi level was observed around the Brillouin zone center in the superconducting state. It is under debate whether this is the evidence on the presence of the BCS-BEC crossover in the superconductor. High-resolution laser-based angle-resolved photoemission measurements are carried out on high quality single crystals of FeSe0…
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In iron-based superconductor Fe(Se,Te), a flat band-like feature near the Fermi level was observed around the Brillouin zone center in the superconducting state. It is under debate whether this is the evidence on the presence of the BCS-BEC crossover in the superconductor. High-resolution laser-based angle-resolved photoemission measurements are carried out on high quality single crystals of FeSe0.45Te0.55 superconductor to address the issue. By employing different polarization geometries, we have resolved and isolated the dyz band and the topological surface band, making it possible to study their superconducting behaviors separately. The dyz band alone does not form a flat band-like feature in the superconducting state and the measured dispersion can be well described by the BCS picture. We find that the flat band-like feature is formed from the combination of the dyz band and the topological surface state band in the superconducting state. These results reveal the origin of the flat band-like feature and rule out the presence of BCS-BEC crossover in Fe(Se,Te) superconductor.
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Submitted 30 July, 2024;
originally announced July 2024.
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Imaginary-time relaxation quantum critical dynamics in two-dimensional dimerized Heisenberg model
Authors:
Jia-Qi Cai,
Yu-Rong Shu,
Xue-Qing Rao,
Shuai Yin
Abstract:
We study the imaginary-time relaxation critical dynamics of the Neel-paramagnetic quantum phase transition in the two-dimensional (2D) dimerized S = 1/2 Heisenberg model. We focus on the scaling correction in the short-time region. A unified scaling form including both short-time and finite-size corrections is proposed. According to this full scaling form, improved short-imaginary-time scaling rel…
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We study the imaginary-time relaxation critical dynamics of the Neel-paramagnetic quantum phase transition in the two-dimensional (2D) dimerized S = 1/2 Heisenberg model. We focus on the scaling correction in the short-time region. A unified scaling form including both short-time and finite-size corrections is proposed. According to this full scaling form, improved short-imaginary-time scaling relations are obtained. We numerically verify the scaling form and the improved short-time scaling relations for different initial states using projector quantum Monte Carlo algorithm.
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Submitted 14 March, 2024;
originally announced March 2024.
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van Hove Singularity-Driven Emergence of Multiple Flat Bands in Kagome Superconductors
Authors:
Hailan Luo,
Lin Zhao,
Zhen Zhao,
Haitao Yang,
Yun-Peng Huang,
Hongxiong Liu,
Yuhao Gu,
Feng Jin,
Hao Chen,
Taimin Miao,
Chaohui Yin,
Chengmin Shen,
Xiaolin Ren,
Bo Liang,
Yingjie Shu,
Yiwen Chen,
Fengfeng Zhang,
Feng Yang,
Shenjin Zhang,
Qinjun Peng,
Hanqing Mao,
Guodong Liu,
Jiangping Hu,
Youguo Shi,
Zuyan Xu
, et al. (5 additional authors not shown)
Abstract:
The newly discovered Kagome superconductors AV$_3$Sb$_5$ (A=K, Rb and Cs) continue to bring surprises in generating unusual phenomena and physical properties, including anomalous Hall effect, unconventional charge density wave, electronic nematicity and time-reversal symmetry breaking. Here we report an unexpected emergence of multiple flat bands in the AV$_3$Sb$_5$ superconductors. By performing…
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The newly discovered Kagome superconductors AV$_3$Sb$_5$ (A=K, Rb and Cs) continue to bring surprises in generating unusual phenomena and physical properties, including anomalous Hall effect, unconventional charge density wave, electronic nematicity and time-reversal symmetry breaking. Here we report an unexpected emergence of multiple flat bands in the AV$_3$Sb$_5$ superconductors. By performing high-resolution angle-resolved photoemission (ARPES) measurements, we observed four branches of flat bands that span over the entire momentum space. The appearance of the flat bands is not anticipated from the band structure calculations and cannot be accounted for by the known mechanisms of flat band generation. It is intimately related to the evolution of van Hove singularities. It is for the first time to observe such emergence of multiple flat bands in solid materials. Our findings provide new insights in revealing the underlying mechanism that governs the unusual behaviors in the Kagome superconductors. They also provide a new pathway in producing flat bands and set a platform to study the flat bands related physics.
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Submitted 9 March, 2024;
originally announced March 2024.
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Relaxation Critical Dynamics with Emergent Symmetry
Authors:
Yu-Rong Shu,
Ting Liao,
Shuai Yin
Abstract:
Universal critical properties can manifest themselves not only in spatial but also in temporal directions. It has been found that critical point with emergent symmetry exhibits intriguing spatial critical properties characterized by two divergent length scales, attracting long-term investigations. However, how the temporal critical properties are affected by emergent symmetry is largely unknown. H…
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Universal critical properties can manifest themselves not only in spatial but also in temporal directions. It has been found that critical point with emergent symmetry exhibits intriguing spatial critical properties characterized by two divergent length scales, attracting long-term investigations. However, how the temporal critical properties are affected by emergent symmetry is largely unknown. Here we study the nonequilibrium critical dynamics in the three-dimensional ($3$D) clock model, whose critical point has emergent $U(1)$ symmetry. We find that in contrast to the magnetization $M$, whose relaxation process is described by the usual dynamic exponent $z$ of the $3$D XY universality class, the angular order parameter $φ_q$ shows a remarkable two-stage evolution characterized by different dynamic critical exponents. While in the short-time stage the relaxation dynamics is governed by $z$, in the long-time stage the dynamics is controlled by a new dynamic exponent $z'$. Further scaling analyses confirm that $z'$ is an indispensable dynamic critical exponent. Our results may be detected in the hexagonal RMnO$_3$ (R$=$rare earth) materials experimentally.
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Submitted 30 August, 2024; v1 submitted 10 November, 2023;
originally announced November 2023.
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Nonequilibrium Dynamics of Dirac Quantum Criticality in Imaginary Time
Authors:
Yin-Kai Yu,
Zhi Zeng,
Yu-Rong Shu,
Zi-Xiang Li,
Shuai Yin
Abstract:
Quantum criticality within Dirac fermions harbors a plethora of exotic phenomena, attracting sustained attention in the past decades. Here, we explore the imaginary-time relaxation dynamics in a typical Dirac quantum criticality belonging to chiral Heisenberg universality class. Performing large-scale quantum Monte Carlo simulation, we unveil rich nonequilibrium critical phenomena from different i…
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Quantum criticality within Dirac fermions harbors a plethora of exotic phenomena, attracting sustained attention in the past decades. Here, we explore the imaginary-time relaxation dynamics in a typical Dirac quantum criticality belonging to chiral Heisenberg universality class. Performing large-scale quantum Monte Carlo simulation, we unveil rich nonequilibrium critical phenomena from different initial states. In particular, we identify a non-stationary initial slip evolution characterized by an unconventional negative critical exponent $θ=-0.84(4)$, corroborating the significant impact of fermionic critical fluctuations. Furthermore, we generalize the nonequilibrium scaling theory to incorporate both fermionic and bosonic critical modes, capturing their distinct relaxation behaviors. Armed with the scaling theory, we establish a new framework to investigate fermionic quantum criticality based on short-time dynamics, paving a promising avenue to fathoming quantum criticality in diverse fermionic systems with high efficiency.
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Submitted 25 February, 2026; v1 submitted 16 October, 2023;
originally announced October 2023.
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Equilibration of Topological Defects Near the Deconfined Quantum Multicritical Point
Authors:
Yu-Rong Shu,
Shao-Kai Jian,
Anders W. Sandvik,
Shuai Yin
Abstract:
Deconfined quantum criticality (DQC) arises from fractionalization of quasi-particles and leads to fascinating behaviors beyond the Landau-Ginzburg-Wilson description of phase transitions. Here, we study the critical dynamics when driving a two-dimensional quantum magnet through a weakly first-order transition point near a putative deconfined multicritical point separating antiferromagnetic and sp…
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Deconfined quantum criticality (DQC) arises from fractionalization of quasi-particles and leads to fascinating behaviors beyond the Landau-Ginzburg-Wilson description of phase transitions. Here, we study the critical dynamics when driving a two-dimensional quantum magnet through a weakly first-order transition point near a putative deconfined multicritical point separating antiferromagnetic and spontaneously dimerized ground states. Numerical simulations show that the conventional Kibble-Zurek scaling (KZS) mechanism is inadequate for describing the annealing process. We introduce the concept of dual asymmetric KZS, where both a pseudocritical relaxation time and the deconfinement time enter and the scaling also depends on the driving direction according to a duality principle connecting the topological defects in the two phases. These defects require a much longer time scale for equilibration than the amplitude of the order parameter. Beyond advancing the DQC scenario, our scaling approach provides a new window into out-of-equilibrium criticality with multiple length and time scales.
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Submitted 13 April, 2025; v1 submitted 8 May, 2023;
originally announced May 2023.
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Chiral photonic topological states in Penrose quasicrystals
Authors:
Yingfang Zhang,
Zhihao Lan,
Liyazhou Hu,
Yiqing Shu,
Xun Yuan,
Penglai Guo,
Xiaoling Peng,
Weicheng Chen,
Jianqing Li
Abstract:
Electromagnetic topological edge states typically are created in photonic systems with crystalline symmetry and these states emerge because of the topological feature of bulk Bloch bands in momentum space according to the bulk-edge correspondence principle. In this work, we demonstrate the existence of chiral topological electromagnetic edge states in Penrose-tiled photonic quasicrystals made of m…
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Electromagnetic topological edge states typically are created in photonic systems with crystalline symmetry and these states emerge because of the topological feature of bulk Bloch bands in momentum space according to the bulk-edge correspondence principle. In this work, we demonstrate the existence of chiral topological electromagnetic edge states in Penrose-tiled photonic quasicrystals made of magneto-optical materials, without relying on the concept of bulk Bloch bands in momentum space. Despite the absence of bulk Bloch bands, which naturally defiles the conventional definition of topological invariants in momentum space characterizing these states, such as the Chern number, we show that some bandgaps in these photonic quasicrystals still could host unidirectional topological electromagnetic edge states immune to backscattering in both cylinders-in-air and holes-in-slab configurations. Employing a real-space topological invariant based on the Bott index, our calculations reveal that the bandgaps hosting these chiral topological edge states possess a nontrivial Bott index of $\pm 1$, depending on the direction of the external magnetic field. Our work opens the door to the study of topological states in photonic quasicrystals.
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Submitted 25 April, 2023;
originally announced April 2023.
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Circle fit optimization for resonator quality factor measurements: point redistribution for maximal accuracy
Authors:
Paul G. Baity,
Connor Maclean,
Valentino Seferai,
Joe Bronstein,
Yi Shu,
Tania Hemakumara,
Martin Weides
Abstract:
The control of material loss mechanisms is playing an increasingly important role for improving coherence times of superconducting quantum devices. Such material losses can be characterized through the measurement of planar superconducting resonators, which reflect losses through the resonance's quality factor $Q_l$. The resonance quality factor consists of both internal (material) losses as well…
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The control of material loss mechanisms is playing an increasingly important role for improving coherence times of superconducting quantum devices. Such material losses can be characterized through the measurement of planar superconducting resonators, which reflect losses through the resonance's quality factor $Q_l$. The resonance quality factor consists of both internal (material) losses as well as coupling losses when resonance photons escape back into the measurement circuit. The combined losses are then described as $Q_l^{-1} = \mathrm{Re}\{Q_c^{-1}\} + Q_i^{-1}$, where $Q_c$ and $Q_i$ reflect the coupling and internal quality factors of the resonator, respectively. To separate the relative contributions of $Q_i$ and $Q_c$ to $Q_l$, diameter-correcting circle fits use algebraic or geometric means to fit the resonance signal on the complex plane. However, such circle fits can produce varied results, so to address this issue, we use a combination of simulation and experiment to determine the reliability of a fitting algorithm across a wide range of quality factor values from $Q_i\ll Q_c$ to $Q_c\ll Q_i$. In addition, we develop a novel measurement protocol that can not only reduce fitting errors by factors $\gtrsim 2$ but also mitigates the influence of the measurement background on the fit results. This technique can be generalized for other resonance systems beyond superconducting resonators.
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Submitted 24 November, 2023; v1 submitted 16 January, 2023;
originally announced January 2023.
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Nodal s$_\pm$ Pairing Symmetry in an Iron-Based Superconductor with only Hole Pockets
Authors:
Dingsong Wu,
Junjie Jia,
Jiangang Yang,
Wenshan Hong,
Yingjie Shu,
Taimin Miao,
Hongtao Yan,
Hongtao Rong,
Ping Ai,
Xing Zhang,
Chaohui Yin,
Chenlong Li,
Shenjin Zhang,
Fengfeng Zhang,
Feng Yang,
Zhimin Wang,
Nan Zong,
Lijuan Liu,
Rukang Li,
Xiaoyang Wang,
Qinjun Peng,
Hanqing Mao,
Guodong Liu,
Shiliang Li,
Huiqian Luo
, et al. (4 additional authors not shown)
Abstract:
The origin of the high temperature superconductivity in the iron-based superconductors remains elusive after being extensively studied for more than a decade. Determination of the pairing symmetry is essential in understanding the superconductivity mechanism. In the iron-based superconductors that have hole pockets around the Brillouin zone center and electron pockets around the zone corners, the…
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The origin of the high temperature superconductivity in the iron-based superconductors remains elusive after being extensively studied for more than a decade. Determination of the pairing symmetry is essential in understanding the superconductivity mechanism. In the iron-based superconductors that have hole pockets around the Brillouin zone center and electron pockets around the zone corners, the pairing symmetry is generally considered to be s$_\pm$, endowing a sign change in the superconducting gap between the hole and electron pockets. For the iron-based superconductors with only hole pockets, however, a couple of pairing scenarios have been proposed but the exact symmetry is still highly controversial. Here we report our determination of the pairing symmetry in KFe$_2$As$_2$ which is a prototypical iron-based superconductor with hole pockets both around the zone center and around the zone corners. By taking laser-based angle resolved photoemission measurements with super-high resolution and at ultra-low temperature, we have precisely determined the superconducting gap distribution and identified the locations of the gap nodes on all the Fermi surface around the zone center and the zone corners. The complete superconducting gap structure, in combination with the observation of the spin resonance in neutron scattering, provides strong evidence on the s$_\pm$ pairing symmetry in KFe$_2$As$_2$ with a gap sign reversal between the hole pockets around the zone center and the hole pockets around the zone corners. These results unify the pairing symmetry in the hole-doped iron-based superconductors and point to the spin fluctuation as the pairing glue in generating superconductivity.
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Submitted 7 December, 2022;
originally announced December 2022.
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Electronic Origin of High-Tc Maximization and Persistence in Trilayer Cuprate Superconductors
Authors:
Xiangyu Luo,
Hao Chen,
Yinghao Li,
Qiang Gao,
Chaohui Yin,
Hongtao Yan,
Taimin Miao,
Hailan Luo,
Yingjie Shu,
Yiwen Chen,
Chengtian Lin,
Shenjin Zhang,
Zhimin Wang,
Fengfeng Zhang,
Feng Yang,
Qinjun Peng,
Guodong Liu,
Lin Zhao,
Zuyan Xu,
Tao Xiang,
X. J. Zhou
Abstract:
In high temperature cuprate superconductors, it was found that the superconducting transition temperature Tc depends on the number of CuO2 planes (n) in the structural unit and the maximum Tc is realized in the trilayer system (n=3). It was also found that the trilayer superconductors exhibit an unusual phase diagram that Tc keeps nearly constant in the overdoped region which is in strong contrast…
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In high temperature cuprate superconductors, it was found that the superconducting transition temperature Tc depends on the number of CuO2 planes (n) in the structural unit and the maximum Tc is realized in the trilayer system (n=3). It was also found that the trilayer superconductors exhibit an unusual phase diagram that Tc keeps nearly constant in the overdoped region which is in strong contrast to the Tc decrease usually found in other cuprate superconductors. The electronic origin of the Tc maximization in the trilayer superconductors and its high Tc persistence in the overdoped region remains unclear. By taking high resolution laser-based angle resolved photoemission (ARPES) measurements, here we report our revelation of the microscopic origin of the unusual superconducting properties in the trilayer superconductors. For the first time we have observed the trilayer splitting in Bi2Sr2Ca2Cu3O10+d (Bi2223) superconductor. The observed Fermi surface, band structures, superconducting gap and the selective Bogoliubov band hybridizations can be well described by a three-layer interaction model. Quantitative information of the microscopic processes involving intra- and interlayer hoppings and pairings are extracted. The electronic origin of the maximum Tc in Bi2223 and the persistence of the high Tc in the overdoped region is revealed. These results provide key insights in understanding high Tc superconductivity and pave a way to further enhance Tc in the cuprate superconductors.
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Submitted 12 October, 2022;
originally announced October 2022.
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Imaginary-time Quantum Relaxation Critical Dynamics with Semi-ordered Initial States
Authors:
Zhi-Xuan Li,
Shuai Yin,
Yu-Rong Shu
Abstract:
We explore the imaginary-time relaxation dynamics near quantum critical points with semi-ordered initial states. Different from the case with homogeneous ordered initial states, in which the order parameter $M$ decays homogeneously as $M\propto τ^{-β/νz}$, here $M$ depends on the location $x$, showing rich scaling behaviors. Similar to the classical relaxation dynamics with an initial domain wall…
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We explore the imaginary-time relaxation dynamics near quantum critical points with semi-ordered initial states. Different from the case with homogeneous ordered initial states, in which the order parameter $M$ decays homogeneously as $M\propto τ^{-β/νz}$, here $M$ depends on the location $x$, showing rich scaling behaviors. Similar to the classical relaxation dynamics with an initial domain wall in Model A, which describes the purely dissipative dynamics, here as the imaginary time evolves, the domain wall expands into an interfacial region with growing size. In the interfacial region, the local order parameter decays as $M\propto τ^{-β_1/νz}$, with $β_1$ being an additional dynamic critical exponent. Far away from the interfacial region the local order parameter decays as $M\propto τ^{-β/νz}$ in the short-time stage, then crosses over to the scaling behavior of $M\propto τ^{-β_1/νz}$ when the location $x$ is absorbed in the interfacial region. A full scaling form characterizing these scaling properties is developed. The quantum Ising model in both one and two dimensions are taken as examples to verify the scaling theory. In addition, we find that for the quantum Ising model the scaling function is an analytical function and $β_1$ is not an independent exponent.
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Submitted 8 May, 2023; v1 submitted 8 October, 2022;
originally announced October 2022.
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Dual dynamic scaling in deconfined quantum criticality
Authors:
Yu-Rong Shu,
Shuai Yin
Abstract:
Emergent symmetry is one of the characteristic phenomena in deconfined quantum critical point (DQCP). As its nonequilibrium generalization, the dual dynamic scaling was recently discovered in the nonequilibrium imaginary-time relaxation dynamics in the DQCP of the $J$-$Q_3$ model. In this work, we study the nonequilibrium imaginary-time relaxation dynamics in the $J$-$Q_2$ model, which also hosts…
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Emergent symmetry is one of the characteristic phenomena in deconfined quantum critical point (DQCP). As its nonequilibrium generalization, the dual dynamic scaling was recently discovered in the nonequilibrium imaginary-time relaxation dynamics in the DQCP of the $J$-$Q_3$ model. In this work, we study the nonequilibrium imaginary-time relaxation dynamics in the $J$-$Q_2$ model, which also hosts a DQCP belonging to the same equilibrium universality class. We not only verify the universality of the dual dynamic scaling at the critical point, but also investigate the breakdown and the vestige of the dual dynamic scaling when the tuning parameter is away from the critical point. We also discuss its possible experimental realizations in devices of quantum computers.
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Submitted 21 January, 2022;
originally announced January 2022.
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Narrow-gap Semiconducting Superhard Amorphous Carbon with Superior Toughness
Authors:
Shuangshuang Zhang,
Yingju Wu,
Kun Luo,
Bing Liu,
Yu Shu,
Yang Zhang,
Lei Sun,
Yufei Gao,
Mengdong Ma,
Zihe Li,
Baozhong Li,
Pan Ying,
Zhisheng Zhao,
Wentao Hu,
Vicente Benavides,
Olga P. Chernogorova,
Alexander V. Soldatov,
Julong He,
Dongli Yu,
Bo Xu,
Yongjun Tian
Abstract:
New carbon forms exhibiting extraordinary physico-chemical properties can be generated from nanostructured precursors under extreme pressure. Nevertheless, synthesis of such fascinating materials is often not well understood that results, as is the case of C60 precursor, in irreproducibility of the results and impeding further progress in the materials design. Here the semiconducting amorphous car…
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New carbon forms exhibiting extraordinary physico-chemical properties can be generated from nanostructured precursors under extreme pressure. Nevertheless, synthesis of such fascinating materials is often not well understood that results, as is the case of C60 precursor, in irreproducibility of the results and impeding further progress in the materials design. Here the semiconducting amorphous carbon having bandgaps of 0.1-0.3 eV and the advantages of isotropic superhardness and superior toughness over single-crystal diamond and inorganic glasses are produced from transformation of fullerene at high pressure and moderate temperatures. A systematic investigation of the structure and bonding evolution was carried out by using rich arsenal of complimentary characterization methods, which helps to build a model of the transformation that can be used in further high p,T synthesis of novel nanocarbon systems for advanced applications. The produced amorphous carbon materials have the potential of demanding optoelectronic applications that diamond and graphene cannot achieve
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Submitted 15 June, 2021;
originally announced June 2021.
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Nonequilibrium dynamics in deconfined quantum critical point revealed by imaginary-time evolution
Authors:
Yu-Rong Shu,
Shao-Kai Jian,
Shuai Yin
Abstract:
As proposed to describe putative continuous phase transitions between two ordered phases, the deconfined quantum critical point (DQCP) goes beyond the prevalent Landau-Ginzburg-Wilson (LGW) paradigm since its critical theory is not expressed in terms of the order parameters characterizing either state, but involves fractionalized degrees of freedom and an emergent symmetry. So far, great efforts h…
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As proposed to describe putative continuous phase transitions between two ordered phases, the deconfined quantum critical point (DQCP) goes beyond the prevalent Landau-Ginzburg-Wilson (LGW) paradigm since its critical theory is not expressed in terms of the order parameters characterizing either state, but involves fractionalized degrees of freedom and an emergent symmetry. So far, great efforts have been spent on its equilibrium properties, but the nonequilibrium properties therein are largely unknown. Here we study the nonequilibrium dynamics of the DQCP via the imaginary-time evolution in the two-dimensional (2D) J-Q$_3$ model. We discover fascinating nonequilibrium scaling behaviors hinging on the process of fractionization and the dynamics of emergent symmetry associated with two length scales. Our findings not only constitute a new realm of nonequilibrium criticality in DQCP, but also offer a controllable knob by which to investigate the dynamics in strongly correlated systems.
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Submitted 8 February, 2021;
originally announced February 2021.
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Short-imaginary-time quantum critical dynamics in the J-Q$_3$ spin chain
Authors:
Yu-Rong Shu,
Shuai Yin
Abstract:
We study the short-imaginary-time quantum critical dynamics (SITQCD) in the J-Q$_3$ spin chain, which hosts a quasi-long-range-order phase to a valence bond solid transition. By using the scaling form of the SITQCD with a saturated ordered phase, we are able to locate the critical point at $q_{\rm c}=0.170(14)$. We also obtain the critical initial slip exponent $θ=-0.507(3)$ and the static exponen…
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We study the short-imaginary-time quantum critical dynamics (SITQCD) in the J-Q$_3$ spin chain, which hosts a quasi-long-range-order phase to a valence bond solid transition. By using the scaling form of the SITQCD with a saturated ordered phase, we are able to locate the critical point at $q_{\rm c}=0.170(14)$. We also obtain the critical initial slip exponent $θ=-0.507(3)$ and the static exponent $β/ν=0.498(2)$. More strikingly, we find that the scaling dimension of the initial order parameter $x_{0}$ is close to zero, which suggests that the initial order parameter is a marginal operator. As a result, there is no initial increase behavior of the order parameter in the short-imaginary-time relaxation process for this model, which is very different from the relaxation dynamics in the Ising-type phase transitions. Our numerical results are realized by the projector quantum Monte Carlo algorithm.
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Submitted 22 September, 2020; v1 submitted 21 June, 2020;
originally announced June 2020.
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Experimental evidence of crystal symmetry protection for the topological nodal line semimetal state in ZrSiS
Authors:
C. C. Gu,
J. Hu,
X. L. Chen,
Z. P. Guo,
B. T. Fu,
Y. H. Zhou,
C. An,
Y. Zhou,
R. R. Zhang,
C. Y. Xi,
Q. Y. Gu,
C. Park,
H. Y. Shu,
W. G. Yang,
L. Pi,
Y. H. Zhang,
Y. G. Yao,
Z. R. Yang,
J. H. Zhou,
J. Sun,
Z. Q. Mao,
M. L. Tian
Abstract:
Tunable symmetry breaking plays a crucial role for the manipulation of topological phases of quantum matter. Here, through combined high-pressure magneto-transport measurements, Raman spectroscopy, and X-ray diffraction, we demonstrate a pressure-induced topological phase transition in nodal-line semimetal ZrSiS. Symmetry analysis and first-principles calculations suggest that this pressure-induce…
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Tunable symmetry breaking plays a crucial role for the manipulation of topological phases of quantum matter. Here, through combined high-pressure magneto-transport measurements, Raman spectroscopy, and X-ray diffraction, we demonstrate a pressure-induced topological phase transition in nodal-line semimetal ZrSiS. Symmetry analysis and first-principles calculations suggest that this pressure-induced topological phase transition may be attributed to weak lattice distortions by non-hydrostatic compression, which breaks some crystal symmetries, such as the mirror and inversion symmetries. This finding provides some experimental evidence for crystal symmetry protection for the topological semimetal state, which is at the heart of topological relativistic fermion physics.
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Submitted 18 November, 2019;
originally announced November 2019.
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Electrochemically-stable ligands bridge photoluminescence-electroluminescence gap of quantum dots
Authors:
Chaodan Pu,
Xingliang Dai,
Yufei Shu,
Meiyi Zhu,
Yunzhou Deng,
Yizheng Jin,
Xiaogang Peng
Abstract:
Colloidal quantum dots (QDs) are promising emitters for electroluminescence devices (QD light-emitting-diodes, QLEDs). Though QDs have been synthesized with efficient and stable photoluminescence, inheriting their superior luminescence in QLEDs remains challenging. This is commonly attributed to unbalanced charge injection and/or interfacial exciton quenching in the devices, instead of lack of sui…
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Colloidal quantum dots (QDs) are promising emitters for electroluminescence devices (QD light-emitting-diodes, QLEDs). Though QDs have been synthesized with efficient and stable photoluminescence, inheriting their superior luminescence in QLEDs remains challenging. This is commonly attributed to unbalanced charge injection and/or interfacial exciton quenching in the devices, instead of lack of suited QD materials. Here, a general but previously overlooked degradation channel in QLEDs, i.e., operando electrochemical reactions of surface ligands with injected charge carriers, is identified after systematic studies of various combination of core/shell QDs and ligands. Applying electrochemically-inert ligands to highly photoluminescent QDs is developed to bridge their photoluminescence-electroluminescence gap. This material-design principle is general for boosting electroluminescence efficiency and lifetime of the QLEDs, resulting in record-long operational lifetimes for both red-emitting QLEDs (T95 > 3800 hours at 1000 cd m-2) and blue-emitting QLEDs (T50 >10,000 hours at 100 cd m-2). Our study provides a critical guideline for the QDs to be used in optoelectronic and electronic devices.
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Submitted 20 October, 2019;
originally announced October 2019.
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Magnetic deformation theory of a vesicle
Authors:
Yao-Gen Shu,
Zhong-Can Ou-Yang
Abstract:
We have extended the Helfrich's spontaneous curvature model [M. Iwamoto and Z. C. Ou-Yang. Chem. Phys. Lett. \textbf{590}(2013)183; Y. X. Deng, et.al., EPL. \textbf{123}(2018)68002] of the equilibrium vesicle shapes by adding the interaction between magnetic field and the constituent molecules to explain the phenomena of the reversibly deformation of artificial stomatocyte[P. G. van Rhee, et.al.,…
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We have extended the Helfrich's spontaneous curvature model [M. Iwamoto and Z. C. Ou-Yang. Chem. Phys. Lett. \textbf{590}(2013)183; Y. X. Deng, et.al., EPL. \textbf{123}(2018)68002] of the equilibrium vesicle shapes by adding the interaction between magnetic field and the constituent molecules to explain the phenomena of the reversibly deformation of artificial stomatocyte[P. G. van Rhee, et.al., Nat. Commun. \textbf{Sep 24;5:5010}(2014)doi: 10.1038/ncomms6010.] and the anharmonic deformation of a self-assembled nanocapsules of bola-amphiphilic molecules and the linear birefringence[O.V. Manyuhina, et.al., Phys. Rev. Lett. \textbf{98}(2007)146101.]. However, the sophistic mathematics in differential geometry is still covered. Here, we present the derivations of formulas in detailed to reveal the perturbation of deformation $ψ$ under two cases.
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Submitted 9 October, 2019;
originally announced October 2019.
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The template-specific fidelity of DNA replication with high-order neighbor effects: a first-passage approach
Authors:
Qiu-Shi Li,
Pei-Dong Zheng,
Yao-Gen Shu,
Zhong-Can Ou-Yang,
Ming Li
Abstract:
DNA replication fidelity is a critical issue in molecular biology. Biochemical experiments have provided key insights on the mechanism of fidelity control by DNAP in the past decades, whereas systematic theoretical studies on this issue began only recently. Because of the underlying difficulties of mathematical treatment, comprehensive surveys on the template-specific replication kinetics are stil…
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DNA replication fidelity is a critical issue in molecular biology. Biochemical experiments have provided key insights on the mechanism of fidelity control by DNAP in the past decades, whereas systematic theoretical studies on this issue began only recently. Because of the underlying difficulties of mathematical treatment, comprehensive surveys on the template-specific replication kinetics are still rare. Here we proposed a first-passage approach to address this problem, in particular the positional fidelity, for complicated processes with high-order neighbor effects. Under biologically-relevant conditions, we derived approximate analytical expressions of the positional fidelity which shows intuitively how some key kinetic pathways are coordinated to guarantee the high fidelity, as well as the high velocity, of the replication processes. It was also shown that the fidelity at any template position is dominantly determined by the nearest-neighbor template sequences, which is consistent with the idea that replication mutations are randomly distributed in the genome.
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Submitted 8 April, 2019; v1 submitted 5 January, 2019;
originally announced January 2019.
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Dynamical properties of the $S=\frac{1}{2}$ random Heisenberg chain
Authors:
Yu-Rong Shu,
Maxime Dupont,
Dao-Xin Yao,
Sylvain Capponi,
Anders W. Sandvik
Abstract:
We use numerical techniques to study dynamical properties at finite temperature ($T$) of the Heisenberg spin chain with random exchange couplings, which realizes the random singlet (RS) fixed point in the low-energy limit. Specifically, we study the dynamic spin structure factor $S(q,ω)$, which can be probed directly by inelastic neutron scattering experiments and, in the limit of small $ω$, in nu…
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We use numerical techniques to study dynamical properties at finite temperature ($T$) of the Heisenberg spin chain with random exchange couplings, which realizes the random singlet (RS) fixed point in the low-energy limit. Specifically, we study the dynamic spin structure factor $S(q,ω)$, which can be probed directly by inelastic neutron scattering experiments and, in the limit of small $ω$, in nuclear magnetic resonance (NMR) experiments through the spin-lattice relaxation rate $1/T_1$. Our work combines three complementary methods: exact diagonalization, matrix-product-state algorithms, and stochastic analytic continuation of quantum Monte Carlo results in imaginary time. Unlike the uniform system, whose low-energy excitations at low $T$ are restricted to $q$ close to $0$ and $π$, our study reveals a continuous narrow band of low-energy excitations in $S(q,ω)$, extending throughout the Brillouin zone. Close to $q=π$, the scaling properties of these excitations are well captured by the RS theory, but we also see disagreements with some aspects of the predicted $q$-dependence further away from $q=π$. Furthermore we find spin diffusion effects close to $q=0$ that are not contained within the RS theory but give non-negligible contributions to the mean $1/T_1$. To compare with NMR experiments, we consider the distribution of the local $1/T_1$ values, which is broad, approximately described by a stretched exponential. The mean value first decreases with $T$, but starts to increase and diverge below a crossover temperature. Although a similar divergent behavior has been found for the static uniform susceptibility, this divergent behavior of $1/T_1$ has never been seen in experiments. Our results show that the divergence of the mean $1/T_1$ is due to rare events in the disordered chains and is concealed in experiments, where the typical $1/T_1$ value is accessed.
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Submitted 29 March, 2018; v1 submitted 5 December, 2017;
originally announced December 2017.
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Universal short time quantum critical dynamics of finite size systems
Authors:
Yu-Rong Shu,
Shuai Yin,
Dao-Xin Yao
Abstract:
We investigate the short time quantum critical dynamics in the imaginary time relaxation processes of finite size systems. Universal scaling behaviors exist in the imaginary time evolution and in particular, the system undergoes a critical initial slip stage characterized by an exponent $θ$, in which an initial power-law increase emerges in the imaginary time correlation function when the initial…
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We investigate the short time quantum critical dynamics in the imaginary time relaxation processes of finite size systems. Universal scaling behaviors exist in the imaginary time evolution and in particular, the system undergoes a critical initial slip stage characterized by an exponent $θ$, in which an initial power-law increase emerges in the imaginary time correlation function when the initial state has zero order parameter and vanishing correlation length. Under different initial conditions, the quantum critical point and critical exponents can be determined from the universal scaling behaviors. We apply the method to the one- and two-dimensional transverse field Ising models using quantum Monte Carlo simulations. In the one-dimensional case, we locate the quantum critical point at $(h/J)_{c}=1.00003(8)$ \thirdrevise{in the thermodynamic limit}, and estimate the critical initial slip exponent $θ=0.3734(2)$, static exponent $β/ν=0.1251(2)$ \thirdrevise{by analyzing data on chains of length $L=32\sim 256$ and $L=48\sim 256$, respectively}. For the two-dimensional square-lattice system, the critical coupling ratio is given by $3.04451(7)$ \thirdrevise{in the thermodynamic limit} while the critical exponents are \thirdrevise{$θ=0.209(4)$ and $β/ν=0.518(1)$ estimated by data on systems of size $L=24\sim 64$ and $L=32\sim 64$, correspondingly.} Remarkably, the critical initial slip exponents obtained in both models are notably distinct from their classical counterparts, owing to the essential differences between classical and quantum dynamics. The short time critical dynamics and the imaginary time relaxation QMC approach can be readily adapted to various models.
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Submitted 18 September, 2017; v1 submitted 16 May, 2017;
originally announced May 2017.
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Properties of the random-singlet phase: from the disordered Heisenberg chain to an amorphous valence-bond solid
Authors:
Yu-Rong Shu,
Dao-Xin Yao,
Chih-Wei Ke,
Yu-Cheng Lin,
Anders W. Sandvik
Abstract:
We use a strong-disorder renormalization group (SDRG) method and ground-state quantum Monte Carlo (QMC) simulations to study S=1/2 spin chains with random couplings, calculating disorder-averaged spin and dimer correlations. The QMC simulations demonstrate logarithmic corrections to the power-law decaying correlations obtained with the SDRG scheme. The same asymptotic forms apply both for systems…
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We use a strong-disorder renormalization group (SDRG) method and ground-state quantum Monte Carlo (QMC) simulations to study S=1/2 spin chains with random couplings, calculating disorder-averaged spin and dimer correlations. The QMC simulations demonstrate logarithmic corrections to the power-law decaying correlations obtained with the SDRG scheme. The same asymptotic forms apply both for systems with standard Heisenberg exchange and for certain multi-spin couplings leading to spontaneous dimerization in the clean system. We show that the logarithmic corrections arise in the valence-bond (singlet pair) basis from a contribution that can not be generated by the SDRG scheme. In the model with multi-spin couplings, where the clean system dimerizes spontaneously, random singlets form between spinons localized at domain walls in the presence of disorder. This amorphous valence-bond solid is asymptotically a random-singlet state and only differs from the random-exchange Heisenberg chain in its short-distance properties.
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Submitted 1 December, 2016; v1 submitted 14 March, 2016;
originally announced March 2016.
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Proofreading of DNA Polymerase: a new kinetic model with higher-order terminal effects
Authors:
Yong-Shun Song,
Yao-Gen Shu,
Xin Zhou,
Zhong-Can Ou-Yang,
Ming Li
Abstract:
The fidelity of DNA replication by DNA polymerase (DNAP) has long been an important issue in biology. While numerous experiments have revealed details of the molecular structure and working mechanism of DNAP which consists of both a polymerase site and an exonuclease (proofreading) site, there were quite few theoretical studies on the fidelity issue. The first model which explicitly considered bot…
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The fidelity of DNA replication by DNA polymerase (DNAP) has long been an important issue in biology. While numerous experiments have revealed details of the molecular structure and working mechanism of DNAP which consists of both a polymerase site and an exonuclease (proofreading) site, there were quite few theoretical studies on the fidelity issue. The first model which explicitly considered both sites was proposed in 1970s' and the basic idea was widely accepted by later models. However, all these models did not systematically and rigorously investigate the dominant factor on DNAP fidelity, i.e, the higher-order terminal effects through which the polymerization pathway and the proofreading pathway coordinate to achieve high fidelity. In this paper, we propose a new and comprehensive kinetic model of DNAP based on some recent experimental observations, which includes previous models as special cases. We present a rigorous and unified treatment of the corresponding steady-state kinetic equations of any-order terminal effects, and derive analytical expressions for fidelity in terms of kinetic parameters under bio-relevant conditions. These expressions offer new insights on how the the higher-order terminal effects contribute substantially to the fidelity in an order-by-order way, and also show that the polymerization-and-proofreading mechanism is dominated only by very few key parameters. We then apply these results to calculate the fidelity of some real DNAPs, which are in good agreements with previous intuitive estimates given by experimentalists.
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Submitted 7 May, 2016; v1 submitted 8 March, 2016;
originally announced March 2016.
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Coexistence of multiple metastable polytypes in rhombohedral bismuth
Authors:
Yu Shu,
Wentao Hu,
Zhongyuan Liu,
Guoyin Shen,
Bo Xu,
Zhisheng Zhao,
Julong He,
Yanbin Wang,
Yongjun Tian,
Dongli Yu
Abstract:
Derivative structural polytypes coexisting with the rhombohedral A7 structure of elemental bismuth (Bi) have been discovered at ambient condition, based on microstructure analyses of pure Bi samples treated under high pressure and high temperature conditions. Three structures with atomic positions close to those of the A7 structure have been identified through first-principles calculations, showin…
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Derivative structural polytypes coexisting with the rhombohedral A7 structure of elemental bismuth (Bi) have been discovered at ambient condition, based on microstructure analyses of pure Bi samples treated under high pressure and high temperature conditions. Three structures with atomic positions close to those of the A7 structure have been identified through first-principles calculations, showing these polytypes energetically comparable to the A7 structure under ambient condition. Simulated diffraction data are in excellent agreement with the experimental observations. We argue that previously reported variations in physical properties (e.g., density, melting point, electrical conductivity, and magnetism) in bismuth could be due to the formation of these polytypes. The coexistence of metastable derivative structural polytypes may be a widely occurring phenomenon in other elemental materials
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Submitted 21 August, 2015;
originally announced August 2015.
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A general theory of kinetics and thermodynamics of steady-state copolymerization
Authors:
Yao-Gen Shu,
Yong-Shun Song,
Zhong-Cun Ou-Yang,
Ming Li
Abstract:
Kinetics of steady-state copolymerization has been investigated since 1940s. Irreversible terminal and penultimate models were successfully applied to a number of comonomer systems, but failed for systems where depropagation is significant. Although a general mathematical treatment of the terminal model with depropagation was established in 1980s, penultimate model and higher-order terminal models…
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Kinetics of steady-state copolymerization has been investigated since 1940s. Irreversible terminal and penultimate models were successfully applied to a number of comonomer systems, but failed for systems where depropagation is significant. Although a general mathematical treatment of the terminal model with depropagation was established in 1980s, penultimate model and higher-order terminal models with depropagation have not been systematically studied, since depropagation leads to hierarchically-coupled and unclosed kinetic equations which are hard to be solved analytically. In this work, we propose a truncation method to solve the steady-state kinetic equations of any-order terminal models with depropagation in an unified way, by reducing them into closed steady-state equations which give the exact solution of the original kinetic equations. Based on the steady-state equations, we also derive a general thermodynamic equality in which the Shannon entropy of the copolymer sequence is explicitly introduced as part of the free energy dissipation of the whole copolymerization system.
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Submitted 9 January, 2015; v1 submitted 19 December, 2014;
originally announced December 2014.