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Spin-polarized pairing induced by the magnetic field in the Bernal bilayer graphene

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Chinese Physics B 2024年第4期33卷 650-654页

作者：黄妍周涛 Guangdong Basic research Center of Excellence for Structure and Fundamental Interactions of Matter Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum MaterialsSchool of PhysicsGuangdong-Hong Kong Joint Laboratory of Quantum Matterand Frontier Research Institute for PhysicsSouth China Normal UniversityGuangzhou 510006China

Recent experimental findings have demonstrated the occurrence of superconductivity in Bernal bilayer graphene when induced by a magnetic *** this study,we conduct a theoretical investigation of the potential pairing symmetry within this superconducting *** developing a theoretical model,we primarily calculate the free energy of the system with p+ip-wave parallel spin pairing,p+ip-wave anti-parallel spin pairing and d+i d-wave pairing *** results confirm that the magnetic field is indeed essential for generating the *** discover that the p+ip-wave parallel spin pairing leads to a lower free energy for the *** numerical calculations of the energy band structure,zero-energy spectral function and density of states for each of the three pairing symmetries under consideration show a strong consistency with the free energy results.

关键词： superconductivity magnetic field induction pairing symmetry Bernal bilayer graphene

Simulation of optimal work extraction for quantum systems with work storage

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Chinese Physics B 2024年第2期33卷 195-203页

作者：宋鹏飞张旦波 Key laboratory of Atomic and Subatomic Structure and quantum Control(Ministry of Education) and School of PhysicsSouth China Normal UniversityGuangzhou 510006China Guangdong Provincial Key laboratory of quantum Engineering and quantum materials Guangdong–Hong Kong Joint Laboratory of Quantum Matterand Frontier Research Institute for PhysicsSouth China Normal UniversityGuangzhou 510006China

The capacity to extract work from a quantum heat machine is not only of practical value but also lies at the heart of understanding quantum *** this paper,we investigate optimal work extraction for quantum systems with work storage,where extracting work is completed by a unitary evolution on the composite *** consider the physical requirement of energy conservation both strictly and on *** both,we construct their corresponding unitaries and propose variational quantum algorithms for optimal work *** show that maximal work extraction in general can be feasible when energy conservation is satisfied on *** demonstrate with numeral simulations using a continuous-variable work *** work show an implementation of a variational quantum computing approach for simulating work extraction in quantum systems.

关键词： quantum algorithm quantum thermodyanmics

Effect of the mixing of s-wave and chiral p-wave pairings on electrical shot noise properties of normal metal/superconductor tunnel junctions

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Chinese Physics B 2024年第7期33卷 538-545页

作者：胡雨辰胡梁宾 Guangdong Provincial Key laboratory of quantum Engineering and quantum materials School of PhysicsSouth China Normal UniversityGuangzhou 510631China

We study theoretically the electrical shot noise properties of tunnel junctions between a normal metal and a superconductor with the mixture of singlet s-wave and chiral triplet p-wave pairing due to broken inversion symmetry. We investigate how the shot noise properties vary as the relative amplitude between the two parity components in the pairing potential is changed. It is demonstrated that some characteristics of the electrical shot noise properties of such tunnel junctions may depend sensitively on the relative amplitude between the two parity components in the pairing potential, and some significant changes may occur in the electrical shot noise properties when the relative amplitude between the two parity components is varied from the singlet s-wave pairing dominated regime to the chiral triplet p-wave pairing dominated regime. In the chiral triplet p-wave pairing dominated regime, the ratio of noise power to electric current is close to 2e both in the in-gap and in the out-gap region. In the singlet s-wave pairing dominated regime, the value of this ratio is close to 4e in the inner gap region but may reduce to about 2e in the outer gap region as the relative amplitude of the chiral triplet pairing component is increased. The variations of the differential shot noise with the bias voltage also exhibit some significantly different features in different regimes. Such different features can serve as useful diagnostic tools for the determination of the relative magnitude of the two parity components in the pairing potential.

关键词： normal metal/superconductor tunnel junctions shot noise mixing of s-wave and chiral p-wave pairing spin–orbit coupling

Variational quantum algorithms for scanning the complex spectrum of non-Hermitian systems

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Frontiers of physics 2024年第4期19卷 275-285页

作者： Xu-Dan Xie Zheng-Yuan Xue Dan-Bo Zhang Key laboratory of Atomic and Subatomic Structure and quantum Control(Ministry of Education) Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matterand School of PhysicsSouth China Normal UniversityGuangzhou 510006China Guangdong Provincial Key laboratory of quantum Engineering and quantum materials Guangdong–Hong Kong Joint Laboratory of Quantum Matterand Frontier Research Institute for PhysicsSouth China Normal UniversityGuangzhou 510006China

Solving non-Hermitian quantum many-body systems on a quantum computer by minimizing the variational energy is challenging as the energy can be ***,we propose a variational quantum algorithm for solving the non-Hermitian Hamiltonian by minimizing a type of energy variance,where zero variance can naturally determine the eigenvalues and the associated left and right ***,the energy is set as a parameter in the cost function and can be tuned to scan the whole spectrum efficiently by using a two-step optimization *** numerical simulations,we demonstrate the algorithm for preparing the left and right eigenstates,verifying the biorthogonal relations,as well as evaluating the *** also investigate the impact of quantum noise on our algorithm and show that its performance can be largely improved using error mitigation ***,our work suggests an avenue for solving non-Hermitian quantum many-body systems with variational quantum algorithms on near-term noisy quantum computers.

关键词： quantum algorithm non-Hermitian physics quantum manybody systems

Layered kagome compound Na_(2)Ni_(3)S_(4)with topological flat band

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Chinese Physics B 2024年第5期33卷 153-159页

作者：叶君耀林益浩王浩哲宋志达冯济谢韦伟贾爽 International Center for quantum materials School of PhysicsPeking UniversityBeijing 100871China Department of Chemistry Michigan State UniversityMI48824USA Hefei National laboratory Hefei 230088China Interdisciplinary Institute of Light-Element quantum materials and research Center for Light-Element Advanced materials Peking UniversityBeijing 100871China

We report structural and electronic properties of Na_(2)Ni_(3)S_(4),a quasi-two-dimensional compound composed of alternating layers of[Ni_(3)S_(4)]^(2-)and Na^(+).The compound features a remarkable Ni-based kagome lattice with a square planar configuration of four surrounding S atoms for each Ni *** and electrical measurements reveal a weak paramagnetic insulator with a gap of about 0.5 *** band structure calculation highlights a set of topological flat bands of the kagome lattice derived from the rotated dxz-orbital with C_(3)+T symmetry in the presence of crystal-field splitting.

关键词： kagome lattice flat band

Interaction between Surface Acoustic Wave and quantum Hall Effects

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Chinese Physics Letters 2024年第4期41卷 105-109页

作者：刘萧吴蒙蒙王任飞王兴豪张文锋董昱江杜瑞瑞刘阳林熙 International Center for quantum materials Peking UniversityBeijing 100871China Center for Excellence University of Chinese Academy of SciencesBeijing 100190China Hefei National laboratory Hefei 230088China Interdisciplinary Institute of Light-Element quantum materials and research Center for Light-Element Advanced materials Peking UniversityBeijing 100871China

Surface acoustic wave(SAW)is a powerful technique for investigating quantum phases appearing in twodimensional electron *** electrons respond to the piezoelectric field of SAW through screening,attenuating its amplitude,and shifting its velocity,which is described by the relaxation *** this work,we systematically study this interaction using orders of magnitude lower SAW amplitude than those in previous *** high magnetic fields,when electrons form highly correlated states such as the quantum Hall effect,we observe an anomalously large attenuation of SAW,while the acoustic speed remains considerably high,inconsistent with the conventional relaxation *** anomaly exists only when the SAW power is sufficiently low.

关键词： relaxation quantum inconsistent

Progress on the antiferromagnetic topological insulator MnBi2Te4

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National Science Review 2024年第2期11卷 33-49页

作者： Shuai Li Tianyu Liu Chang Liu Yayu Wang Hai-Zhou Lu X.C.Xie Department of Physics Harbin Institute of Technology Shenzhen Institute for quantum Science and Engineering and Department of Physics Southern University of Science and Technology(SUSTech) quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area(Guangdong) Shenzhen Key laboratory of quantum Science and Engineering International quantum Academy Beijing Academy of quantum Information Sciences Beijing Key laboratory of Optoelectronic Functional materials&Micro-Nano Devices Department of Physics Renmin University of China State Key laboratory of Low Dimensional quantum Physics Department of PhysicsTsinghua University Frontier Science Center for quantum Information Hefei National laboratory International Center for quantum materials School of Physics Peking University Institute for Nanoelectronic Devices and quantum Computing Fudan University

Topological materials, which feature robust surface and/or edge states, have now been a research focus in condensed maTher physics. They represent a new class of materials exhibiting nontrivial topological phases,and provide a platform for exploring exotic transport phenomena, such as the quantum anomalous Hall effect and the quantum spin Hall effect. Recently, magnetic topological materials have attracted considerable interests due to the possibility to study the interplay between topological and magnetic *** particular, the quantum anomalous Hall and axion insulator phases can be realized in topological insulators with magnetic order. MnBi2Te4, as the first intrinsic antiferromagnetic topological insulator discovered, allows the examination of existing theoretical predictions; it has been extensively studied, and many new discoveries have been made. Here we review the progress made on MnBi2Te4from both experimental and theoretical aspects. The bulk crystal and magnetic structures are surveyed first, followed by a review of theoretical calculations and experimental probes on the band structure and surface states, and a discussion of various exotic phases that can be realized in MnBi2Te4. The properties of MnBi2Te4thin films and the corresponding transport studies are then reviewed, with an emphasis on the edge state transport. Possible future research directions in this field are also discussed.

关键词： MnBi2Te4 magnetic topological insulator antiferromagnetic quantum anomalous Hall effect axion insulator

Purification of copper foils driven by single crystallization

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Chinese Physics B 2024年第2期33卷 506-511页

作者：寇金宗赵孟泽李兴光何梦林杨方友刘科海成庆秋任云龙刘灿付莹吴慕鸿刘开辉王恩哥 Songshan Lake materials laboratory Dongguan 523808China Beijing National laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China Guangdong Provincial Key laboratory of quantum Engineering and quantum materials School of PhysicsSouth China Normal UniversityGuangzhou 510006China Guangdong–Hong Kong Joint laboratory of quantum Matter Frontier Research Institute for PhysicsSouth China Normal UniversityGuangzhou 510006China State Key laboratory for Mesoscopic Physics Frontiers Science Center for Nano-optoelectronicsSchool of PhysicsPeking UniversityBeijing 100871China Key laboratory of quantum State Construction and Manipulation(Ministry of Education) Department of PhysicsRenmin University of ChinaBeijing 100872China International Center for quantum materials Collaborative Innovation Center of Quantum MatterPeking UniversityBeijing 100871China School of Physics Liaoning UniversityShenyang 110036China

High-purity copper(Cu) with excellent thermal and electrical conductivity, is crucial in modern technological applications, including heat exchangers, integrated circuits, and superconducting magnets. The current purification process is mainly based on the zone/electrolytic refining or anion exchange, however, which excessively relies on specific integrated equipment with ultra-high vacuum or chemical solution environment, and is also bothered by external contaminants and energy consumption. Here we report a simple approach to purify the Cu foils from 99.9%(3N) to 99.99%(4N) by a temperature-gradient thermal annealing technique, accompanied by the kinetic evolution of single crystallization of *** success of purification mainly relies on(i) the segregation of elements with low effective distribution coefficient driven by grain-boundary movements and(ii) the high-temperature evaporation of elements with high saturated vapor *** purified Cu foils display higher flexibility(elongation of 70%) and electrical conductivity(104% IACS) than that of the original commercial rolled Cu foils(elongation of 10%, electrical conductivity of ~ 100% IACS). Our results provide an effective strategy to optimize the as-produced metal medium, and therefore will facilitate the potential applications of Cu foils in precision electronic products and high-frequency printed circuit boards.

关键词： purification copper foil thermal annealing technique single crystallization

Theoretical study of superradiant masing with solid-state spins at room temperature

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Science China(Physics,Mechanics & Astronomy) 2024年第6期67卷 38-47页

作者： Qilong Wu Yuan Zhang Hao Wu Shi-Lei Su Kai-Kai Liu Mark Oxborrow Chong-Xin Shan Klaus Mølmer Henan Key laboratory of Diamond Optoelectronic materials and Devices Key Laboratory of Material Physics Ministry of EducationSchool of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China Institute of quantum materials and Physics Henan Academy of SciencesZhengzhou 450046China Center for quantum Technology research and Key laboratory of Advanced Optoelectronic quantum Architecture and Measurements School of PhysicsBeijing Institute of TechnologyBeijing 100081China Beijing Academy of quantum Information Sciences Beijing 100193China Department of materials Imperial College LondonLondon SW72AZUK Niels Bohr Institute University of CopenhagenCopenhagen 2100Denmark

Steady-state superradiance and superradiant lasing attract significant attentions in the field of optical lattice clocks,but have not been achieved yet due to the technical challenges and atom loss *** this article,we propose that their counter-part may be observed in the microwave domain with solid-state spins,i.e.,nitrogen-vacancy center spins and pentacene molecular spins,coupled to microwave resonator at room temperature with realistic technical *** validate our proposal,we investigate systematically the system dynamics and steady-state by solving quantum master equations for the multi-level and multi-process dynamics of trillions of *** calculations show that the superradiant Rabi oscillations occur firstly due to transitions among different Dicke states,and the subsequent continuous-wave superradiant masing can achieve a linewidth well below *** work may guide further exploration of transient and steady-state superradiant masing with the mentioned and other solid-state spins *** ultra-narrow linewidth may find applications in deep-space communications,radio astronomy and high-precision metrology.

关键词： solid-state spins superradiance maser

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