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arXiv 2024年

作者： Yang, Shengguo Chen, Jiaxin Liu, Chao-Fei Chen, Mingxing Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education School of Physics and Electronics Hunan Normal University Changsha410081 China School of Science Jiangxi University of Science and Technology Ganzhou341000 China State Key Laboratory of Powder Metallurgy Central South University Changsha410083 China

Moiré lattices have served as the ideal quantum simulation platform for exploring novel physics due to the flat electronic bands resulting from the long wavelength moiré potentials. However, the large sizes of this type of system challenge the first-principles methods for full calculations of their electronic structures, thus bringing difficulties in understanding the nature and evolution of the flat bands. In this study, we investigate the electronic structures of moiré patterns of MoSe2/WSe2 by combining ab initio and machine learning methods. We find that a flat band with a bandwidth of about 5 meV emerges below the valence band edge at the K point for the H-stacking at a twist angle of 3.89◦ without spin-orbit coupling effect. Then, it shifts dramatically as the twist angle decreases and becomes about 20 meV higher than the valence band maximum for the twist angle of 3.15◦. Multiple ultra-flat bands emerge as the twist angle is reduced to 1.7◦. The spin-orbit coupling leads to a giant spin splitting comparable to that observed in the untwisted system (about 0.45 eV) and is nearly independent of twisting and stacking. As a result, the K-valley flat band remains the valence band maximum with the inclusion of spin-orbit coupling. Band unfolding reveals that the ultra-flat bands formed by the Γ and K valleys show distinct behaviors. The Γ-valley flat bands are sensitive to the interlayer coupling, thus experiencing dramatic changes as the twist angle decreases. In contrast, the K-valley flat band, which shows a weak dependence on the interlayer coupling, is mainly modulated by structural reconstruction. Therefore, a relatively small angle (2.13◦) is required to generate the K-valley flat band, which experiences a transition from the honeycomb to the triangular lattice as the twist angle decreases. © 2024, CC BY.

关键词： Spin orbit coupling

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Control of a single-photon router via an extra cavity

arXiv

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arXiv 2023年

作者： Luo, Yi-Ke Yang, Ya Lu, Jing Zhou, Lan Synergetic Innovation Center for Quantum Effects and Applications Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education School of Physics and Electronics Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Controllable single-photon routing plays an important role in quantum networks. We investigate single-photon scattering in two one-dimensional (1D) waveguides by a three-level emitter with a cascade configuration, which is a dipole coupled to an extra cavity. The tunneling path for the transmission of a single photon is switched by whether the extra cavity contains photons. For the setup, the Autler-Townes splitting is modulated by the extra cavity, in which the transmission valley (reflection range) width is tunable in terms of the number of photons in the extra cavity. Our investigation will be beneficial to single-photon routing in quantum networks using quantifiable photon numbers in an extra cavity. Copyright © 2023, The Authors. All rights reserved.

关键词： Photons

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An analysis on doubly bottom molecular tetraquarks composed of H(s) and T(s) doublets

arXiv

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arXiv 2025年

作者： Su, Jun-Chao Song, Qing-Fu Lü, Qi-Fang Zhu, Jingya School of Physics and Electronics Henan University Kaifeng475004 China School of Physics Central South University Changsha410083 China Department of Physics Hunan Normal University Changsha410081 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Changsha410081 China Key Laboratory for Matter Microstructure and Function of Hunan Province Hunan Normal University Changsha410081 China

In this work, we investigate the doubly bottom H(s)T¯(s) and H(s)T(s) systems by adopting the one-boson-exchange model, where H(s) and T(s) represent S -wave (formula presented) and P-wave (formula presented) doublets, respectively. For the HT¯ systems, we predict some loosely bound states in the I(JPC) = 0(1−±) BB¯1, (formula presented), I(JPC) = 0(1−±) B∗B¯1 and (formula presented) channels, which are the most promising hidden bottom molecular tetraquarks. For the HT systems, the I(JP) = 0(1−) B∗B1 and (formula presented) channels are also likely to form molecular tetraquarks. In contrast, no molecular candidates have been identified in the bottom-strange sectors. One can hope that our predictions will provide valuable insights to the LHCb and Belle II Collaborations as they continue to explore this fascinating field through experimental research. © 2025, CC BY.

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Nonreciprocal Single-Photon Band Structure in a Coupled-Spinning-Resonator chain

arXiv

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arXiv 2024年

作者： Li, Jing Yang, Ya Xu, Xun-Wei Lu, Jing Jing, Hui Zhou, Lan Key Laboratory of Low-Dimension Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Synergetic Innovation Center for Quantum Effects and Applications Xiangjiang-Laboratory Department of Physics Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China School of Physics and Chemistry Hunan First Normal University Changsha410205 China

We analyze the single-photon band structure and the transport of a single photon in a one-dimensional coupled-spinning-resonator chain. The time-reversal symmetry of the resonators chain is broken by the spinning of the resonators, instead of external or synthetic magnetic field. Two nonreciprocal single-photon band gaps can be obtained in the coupled-spinning-resonator chain, whose width depends on the angular velocity of the spinning resonator. Based on the nonreciprocal band gaps, we can implement a single photon circulator at multiple frequency windows, and the direction of photon cycling is opposite for different band gaps. In addition, reciprocal single-photon band structures can also be realized in the coupled-spinning-resonator chain when all resonators rotate in the same direction with equal angular velocity. Our work open a new route to achieve, manipulate, and switch nonreciprocal or reciprocal single-photon band structures, and provides new opportunities to realize novel single-photon devices. Copyright © 2024, The Authors. All rights reserved.

关键词： Resonators

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Universal inverse electrocaloric effect in perovskites

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Physical Review B 2023年第18期107卷 184105-184105页

作者： Xingyue Ma Mingxing Chen Jun-Ming Liu Di Wu Yurong Yang National Laboratory of Solid State Microstructures and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China Jiangsu Key Laboratory of Artificial Functional Materials Department of Materials Science and Engineering Nanjing University Nanjing 210093 China School of Physics and Electronics Hunan Normal University Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Changsha 410081 People's Republic of China

The electrocaloric effect (ECE) offers a promising alternative to the traditional gas compressing refrigeration due to its high efficiency and environmental friendliness. The unusual inverse (negative) electrocaloric effect refers to the adiabatic temperature drops due to the application of electric field, in contrast with the normal (positive) ECE, and provides ways to reach a larger temperature span in refrigeration cycles by combining the normal and inverse ECE. However, the inverse ECE is unusual and requires a clear understanding of microscopic mechanisms. Here, we found the unexpected and extensive inverse ECE in nonpolar orthorhombic, tetragonal, and cubic phases of halide and oxide perovskite at a wide temperature range by means of first-principle-based large-scale Monte Carlo methods. Such an unexpected inverse ECE originates from the octahedral tilting related entropy change rather than the polarization entropy change under the application of electric field. Furthermore, a giant inverse ECE with temperature change of 8.6 K is found at room temperature. This giant and extensive inverse ECE in perovskite opens up a new horizon in the research of caloric effects and broadens the electrocaloric refrigeration ways with high efficiency.

关键词： Electrocaloric effect Entropy Percolation Perovskites Hybrid Monte Carlo algorithm

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Cavity Modified Oscillating Bound States with a Λ-type giant emitter in a linear waveguide

arXiv

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arXiv 2024年

作者： Sun, Ge Yang, Ya Li, Jing Lu, Jing Zhou, Lan Key Laboratory of Low-Dimension Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Synergetic Innovation Center for Quantum Effects and Applications Xiangjiang-Laboratory Department of Physics Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China School of Physics and Chemistry Hunan First Normal University Changsha410205 China

We study a system composed by a three-level giant atom (3GA), a waveguide initially in the vacuum state, and a single-mode cavity. The 3GA-cavity system is in a strong-coupling regime, and the distance between the coupling points is comparable to the coherent length of a spontaneously emitted photon. The dynamics of the 3GA and its radiative field in the waveguide for long time are analyzed. Besides the steady value, we also found an oscillatory character of the excited state population, a signature of oscillating bound states which is generated by the superposition of two bound states in the continuum. The radiative field propagates in the cavity-like geometry formed by the coupling points. When one bound state is emergent, a sine-like interference pattern is visible for the emitted field intensity in spacetime. An oscillatory character in time and a beat in space for the emitted field intensity are observed when two bound states are emergent in a subspace. The wavelengths and the periods are controlled by the number of the photons in the cavity. Copyright © 2024, The Authors. All rights reserved.

关键词： Excited states

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Entangling two giant atoms via a topological waveguide

arXiv

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arXiv 2023年

作者： Luo, Wen-Bin Yin, Xian-Li Liao, Jie-Qiao Liao, Jie-Qiao Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

The entanglement generation of two two-level giant atoms coupled to a photonic waveguide, which is formed by a Su–Schrieffer–Heeger (SSH) type coupled-cavity array is studied. Here, each atom is coupled to the waveguide through two coupling points. The two-atom separate-coupling case is studied, and 16 coupling configurations are considered for the coupling-point distributions between the two atoms and the waveguide. Quantum master equations are derived to govern the evolution of the two atoms and characterize atomic entanglement by calculating the concurrence of the two-atom states. It is found that the two giant-atom entanglement depends on the coupling configurations and the coupling-point distance of the giant atoms. In particular, the entanglement dynamics of the two giant atoms in 14 coupling configurations depend on the dimerization parameter of the SSH waveguide. According to the self-energies of the two giant atoms, it is found that ten of these 16 coupling configurations can be divided into five pairs. It is also showed that the delayed sudden birth of entanglement between the two giant atoms is largely enhanced in these five pairs of coupling configurations. This work will promote the study of quantum effects and coherent manipulation in giant-atom topological-waveguide-QED systems. Copyright © 2023, The Authors. All rights reserved.

关键词： Atoms

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Insights into varicella-zoster virus assembly from the B-and C-capsid at near-atomic resolution structures

微生物与宿主健康（英文）

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微生物与宿主健康（英文） 2024年第2期2卷 64-74页

作者： Lei Cao Nan Wang Zhe Lv Wenyuan Chen Zhonghao Chen Lifei Song Xueyan Sha Guiqiang Wang Yaling Hu Xiaojun Lian Guoliang Cui Jinyan Fan Yaru Quan Hongrong Liu Hai Hou Xiangxi Wang CAS Key Laboratory of Infection and Immunity National Laboratory of MacromoleculesInstitute of BiophysicsChinese Academy of SciencesBeijingChina Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-dimensional Quantum Structures and Quantum ControlSchool of Physics and ElectronicsHunan Normal UniversityHunanChina Institute of Medical Research Northwestern Polytechnical UniversityShanxiChina Sinovac(Dalian)Vaccine Technology Co. Ltd.LiaoningChina Sinovac Biotech Ltd. BeijingChina National Institutes for Food and Drug Control BeijingChina

Varicella-zoster is a highly communicable virus that can be transmitted through the airborne *** one quarter of people are infected with this *** studies have described the structure of A-capsid and a blurred reconstruc-tion of the C-capsid with icosahedral *** this study,we have determined the more precise detailed structures of the varicella-zoster virus(VZV)B-and C-capsid in icosahedral symmetry using a combination of block-based recon-struction and symmetry relaxation *** addition,we are reporting structural details of the portal vertex recon-structions in five-fold symmetry and portal reconstructions in twelve-fold *** structures unveil the basis for the high thermal stability of the VZV *** conformational flexibility of structural elements of the capsid plays a role in the assembly of the capsid and drives processes critical for the viral life *** results of the study open up new avenues for the development of drugs against a highly prevalent and contagious pathogen.

关键词： varicella-zoster virus capsid structure virus assembly

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Dark-Mode Theorems for Quantum Networks

arXiv

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arXiv 2023年

作者： Huang, Jian Liu, Cheng Xu, Xun-Wei Liao, Jie-Qiao Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

We propose and prove two theorems for determining the number of dark modes in linear two-component quantum networks composed of two types of bosonic modes. This is achieved by diagonalizing the two sub-networks of the same type of modes, mapping the networks to either a standard or a thick arrowhead matrix, and analyzing the linear dependence and independence between the column vectors associated with degenerate normal modes in the coupling matrix. We confirm the two theorems by checking the simultaneous ground-state cooling of the mechanical modes in linearized optomechanical networks. These results also work for linear fermionic networks and other networks described by quadratic coupled-mode Hamiltonian. The present method can be extended to study the dark-state effect in driven atom systems and to construct large decoherence-free subspaces for processing quantum information. This work will initiate the studies on dynamical, transport, and statistical properties of linear networks with decoupled subspaces. Copyright © 2023, The Authors. All rights reserved.

关键词： Linear networks

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Simultaneous ground-state cooling of two levitated nanoparticles by coherent scattering

arXiv

引用

arXiv 2023年

作者： Xu, Yi Liu, Yu-Hong Liu, Cheng Liao, Jie-Qiao Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Simultaneous ground-state cooling of two levitated nanoparticles is a crucial prerequisite for investigation of macroscopic quantum effects such as quantum entanglement and quantum correlation involving translational motion of particles. Here we consider a coupled cavity-levitated-particle system and present a detailed derivation of its Hamiltonian. We find that the y-direction motions of the two particles are decoupled from the cavity field and both the x- and z-direction motions, and that the z-direction motions can be further decoupled from the cavity field and the x-direction motions by choosing proper locations of the particles. We study the simultaneous cooling of these mechanical modes in both the three-mode and five-mode cavity-levitated optomechanical models. It is found that there exists a dark-mode effect when the two tweezers have the same powers, which suppress the simultaneous ground-state cooling. Nevertheless, the simultaneous ground-state cooling of these modes can be realized by breaking the dark-mode effect under proper parameters. Our system provides a versatile platform to study quantum effects and applications in cavity-levitated optomechanical systems. Copyright © 2023, The Authors. All rights reserved.

关键词： Nanoparticles

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