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Impurity effects in one dimensional spin nematic liquid

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arXiv 2024年

作者： Nakamura, Fumiya Tada, Yasuhiro Quantum Matter Program Graduate School of Advanced Science and Engineering Hiroshima University Hiroshima Higashihiroshima739-8530 Japan Institute for Solid State Physics University of Tokyo Kashiwa277-8581 Japan

We study impurity effects in the spin nematic phase of the S = 1/2 J1-J2 frustrated spin chain under an external magnetic field by using the infinite density matrix renormalization group and the bosonization. It is found that local magnetization almost saturates around the impurity and the entanglement entropy nearly vanishes at the corresponding bonds, not only when the magnetic interactions near the impurity are weakened but also when they are strengthened compared to those in the bulk. Then, we examine spin correlations and Friedel oscillations induced by the impurity. The bosonization provides a qualitative understanding of the characteristic behaviors of the magnetization. We also discuss impacts of the impurity on experiments by focusing on NMR spectra. Copyright © 2024, The Authors. All rights reserved.

关键词： Magnetization

Quantized polarization in a generalized Rice-Mele model at arbitrary filling

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arXiv 2024年

作者： Tada, Yasuhiro Quantum Matter Program Graduate School of Advanced Science and Engineering Hiroshima University Hiroshima Higashihiroshima739-8530 Japan Institute for Solid State Physics University of Tokyo Kashiwa277-8581 Japan

We discuss the charge polarization in a generalized Rice-Mele model at arbitrary particle filling per site as a model of charge ordered systems in one dimension. The model possesses neither the conventional bond-centered inversion symmetry nor the one site translation symmetry alone, but has combinations of these symmetries. We show that the charge polarization in the ground state is quantized by the combined symmetry and is characterized solely by the filling. Especially, the polarization can be 1/2 (mod 1) in the zero filling limit. Under the open boundary condition, there exist excess charges accumulated near edges of the system irrespective of existence or absence of edge modes. Correspondingly, we decompose the polarization into a bulk contribution and an edge contribution, and numerically demonstrate that the polarization is dominated by the former (latter) when the energy gap is small (large). We also discuss a simple generalization of our model and examine absence/existence of a gapless edge mode protected by the inversion symmetry by introducing intra unit cell and inter unit cell contributions of the charge polarization. Copyright © 2024, The Authors. All rights reserved.

关键词： Polarization

Unified Variational Approach Description of Ground-State Phases of the Two-Dimensional Electron Gas

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Physical Review Letters 2024年第26期133卷 266504-266504页

作者： Conor Smith Yixiao Chen (陈一潇) Ryan Levy Yubo Yang (杨煜波) Miguel A. Morales Shiwei Zhang Center for Computational Quantum Physics Flatiron Institute New York New York 10010 USA Department of Electrical and Computer Engineering University of New Mexico Albuquerque New Mexico 87131 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

The two-dimensional electron gas (2DEG) is a fundamental model, which is drawing increasing interest because of recent advances in experimental and theoretical studies of 2D materials. Current understanding of the ground state of the 2DEG relies on quantum Monte Carlo calculations, based on variational comparisons of different Ansätze for different phases. We use a single variational ansatz, a general backflow-type wave function using a message-passing neural quantum state architecture, for a unified description across the entire density range. The variational optimization consistently leads to lower ground-state energies than previous best results. Transition into a Wigner crystal (WC) phase occurs automatically at rs=37±1, a density lower than currently believed. Between the liquid and WC phases, the same ansatz and variational search strongly suggest the existence of intermediate states in a broad range of densities, with enhanced short-range nematic spin correlations.

关键词： Wave functions

Hunting axion dark matter signatures in low-frequency terrestrial magnetic fields

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arXiv 2025年

作者： Taruya, Atsushi Nishizawa, Atsushi Himemoto, Yoshiaki Center for Gravitational Physics and Quantum Information Yukawa Institute for Theoretical Physics Kyoto University Kyoto606-8502 Japan Kavli Institute for the Physics and Mathematics of the Universe Todai Institutes for Advanced Study The University of Tokyo Kavli IPMU WPI Chiba Kashiwa277-8583 Japan Physics Program Graduate School of Advanced Science and Engineering Hiroshima University Hiroshima Higashi-Hiroshima739-8526 Japan Astrophysical Science Center Hiroshima University Hiroshima Higashi-Hiroshima739-8526 Japan Graduate School of Science The University of Tokyo Tokyo113-0033 Japan Department of Liberal Arts and Basic Sciences College of Industrial Technology Nihon University Chiba Narashino275-8576 Japan

We show that Earth’s natural environment can serve as a powerful probe for ultralight axion dark matter. In the presence of global geomagnetic fields, the axions with masses ranging from 10−15 eV–10−13 eV induce electromagnetic waves in the (sub-) extremely low-frequency band (0.3 − 30 Hz) through the axion-photon coupling. We predict the amplitude of induced magnetic fields in the Earth-ionosphere cavity, taking the finite conductivity of the atmosphere into account. This allows us to constrain the axion-photon coupling parameter, gaγ, from the long-term monitoring data of the low-frequency magnetic fields, resulting in a significant improvement from the previous constraints down to gaγ 4 × 10−13 GeV−1 for axion mass ∼ 3 × 10−14 eV. © 2025, CC BY-NC-ND.

关键词： Geomagnetism

Light-induced Weyl semiconductor-to-metal transition mediated by Peierls instability

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Physical Review B 2022年第20期106卷 205118-205118页

作者： Honglie Ning Omar Mehio Chao Lian Xinwei Li Eli Zoghlin Preston Zhou Bryan Cheng Stephen D. Wilson Bryan M. Wong David Hsieh Institute for Quantum Information and Matter California Institute of Technology Pasadena California 91125 USA Department of Physics California Institute of Technology Pasadena California 91125 USA Department of Chemical and Environmental Engineering Materials Science and Engineering Program and Department of Physics and Astronomy University of California Riverside California 92521 USA Materials Department University of California Santa Barbara California 93106 USA

Elemental tellurium is a strongly spin-orbit coupled Peierls-distorted semiconductor whose band structure features topologically protected Weyl nodes. Using time-dependent density functional theory calculations, we show that impulsive optical excitation can be used to transiently control the amplitude of the Peierls distortion, realizing a mechanism to switch tellurium between three states: Weyl semiconductor, Weyl metal, and non-Weyl metal. Further, we present experimental evidence of this inverse Peierls distortion using time-resolved optical second harmonic generation measurements. These results provide a pathway to multifunctional ultrafast Weyl devices and introduce Peierls systems as viable hosts of light-induced topological transitions.

关键词： Electron-phonon coupling Optical phonons Peierls transition Topological materials Topological phase transition Topological phases of matter Density functional theory Optical second-harmonic generation Time-resolved infrared spectroscopy

Automated detection of symmetry-protected subspaces in quantum simulations

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arXiv 2023年

作者： Rotello, Caleb Jones, Eric B. Graf, Peter Kapit, Eliot Department of Physics and Quantum Engineering Program Colorado School of Mines GoldenCO80401 United States National Renewable Energy Laboratory GoldenCO80401 United States Infleqtion LouisvilleCO80027 United States

The analysis of symmetry in quantum systems is of utmost theoretical importance, useful in a variety of applications and experimental settings, and is difficult to accomplish in general. Symmetries imply conservation laws, which partition Hilbert space into invariant subspaces of the time-evolution operator, each of which is demarcated according to its conserved quantity. We show that, starting from a chosen basis, any invariant, symmetry-protected subspaces which are diagonal in that basis are discoverable using transitive closure on graphs representing state-to-state transitions under k-local unitary operations. Importantly, the discovery of these subspaces relies neither upon the explicit identification of a symmetry operator or its eigenvalues nor upon the construction of matrices of the full Hilbert space dimension. We introduce two classical algorithms, which efficiently compute and elucidate features of these subspaces. The first algorithm explores the entire symmetry-protected subspace of an initial state in time complexity linear to the size of the subspace by closing local basis state-to-basis state transitions. The second algorithm determines, with bounded error, if a given measurement outcome of a dynamically-generated state is within the symmetry-protected subspace of the state in which the dynamical system is initialized. We demonstrate the applicability of these algorithms by performing post-selection on data generated from emulated noisy quantum simulations of three different dynamical systems: the Heisenberg-XXX model and the T6 and F4 quantum cellular automata. Due to their efficient computability and indifference to identifying the underlying symmetry, these algorithms lend themselves to the post-selection of quantum computer data, optimized classical simulation of quantum systems, and the discovery of previously hidden symmetries in quantum mechanical systems. © 2023, CC BY.

关键词： Hilbert spaces

Advances in Electron Energy-Loss Spectroscopy with High Spatial and Energy Resolution

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Microscopy and Microanalysis 2014年第S3期20卷 2176-2177页

作者： G. A. Botton E. P. Bellido M. Bugnet N. Gauquelin S. Prabhudev D. Rossouw S. Stambula S.Y. Woo G.-Z. Zhu H. Zhang Department of Materials Science and Engineering McMaster University Hamilton ON Canada Now at EMAT University of Antwerp Antwerp Belgium Now with Department of Materials Science and Metallurgy University of Cambridge UK CIfAR Quantum Materials Program and Dept of Physics Univ. of Toronto Toronto ON Canada

Conformity Experiment on Inelastic Scattering Exponent of Electrons in Two Dimensions

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Physical Review Letters 2024年第9期133卷 096302页

作者： Ching-Chen Yeh Pin-Chi Liao Yanfei Yang Wei-Chen Lin Alireza R. Panna Albert F. Rigosi Randolph E. Elmquist Chi-Te Liang Gaithersburg Maryland 20899 USA Department of Physics Graphene Waves Germantown Maryland 20876 USA Taiwan International Graduate Program Department of Engineering and System Science Center for Quantum Science and Engineering (CQSE) Taiwan Consortium of Emergent Crystalline Materials (TCECM) Taipei 106 Taiwan

The quantum Hall (QH) effect is one of the most widely studied physical phenomenon in two dimensions. The plateau-plateau transition within this effect can be comprehensively described by the scaling theory, which encompasses three pivotal exponents: the critical exponent κ, the inelastic scattering exponent p, and the universal exponent γ. Prior studies have focused on measuring κ and estimating γ, assuming a constant p value of 2 across magnetic fields. Here, our work marks a significant advancement by measuring all three exponents within a single graphene device and a conventional two-dimensional electron system. This study uniquely determines p at low magnetic fields (weak localization region and well outside the QH regime) and high magnetic fields (in the vicinity of the QH regime). Employing a comprehensive analytical approach that includes weak localization, plateau-plateau transitions, and variable range hopping, we have directly determined κ, p, and γ. Our findings reveal a distinct variation in p, shifting from 1 in the low magnetic field regime to 2 in the QH regime in graphene.

关键词： Electrical properties Fermions Landau levels quantum interference effects quantum phase transitions

Fractional Integrable Nonlinear Soliton Equations

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Physical Review Letters 2022年第18期128卷 184101-184101页

作者： Mark J. Ablowitz Joel B. Been Lincoln D. Carr Department of Applied Mathematics University of Colorado Boulder Colorado 80309 USA Department of Applied Mathematics and Statistics Colorado School of Mines Golden Colorado 80401 USA Department of Physics Colorado School of Mines Golden Colorado 80401 USA Quantum Engineering Program Colorado School of Mines Golden Colorado 80401 USA

Nonlinear integrable equations serve as a foundation for nonlinear dynamics, and fractional equations are well known in anomalous diffusion. We connect these two fields by presenting the discovery of a new class of integrable fractional nonlinear evolution equations describing dispersive transport in fractional media. These equations can be constructed from nonlinear integrable equations using a widely generalizable mathematical process utilizing completeness relations, dispersion relations, and inverse scattering transform techniques. As examples, this general method is used to characterize fractional extensions to two physically relevant, pervasive integrable nonlinear equations: the Korteweg–deVries and nonlinear Schrödinger equations. These equations are shown to predict superdispersive transport of nondissipative solitons in fractional media.

关键词： Solitons