The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced qu...The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced quantum electrodynamics.We used the perturbative renormalization group method to study the low-energy behavior of the system and found that it flows to a fixed point of the non-Fermi liquid composed of relativistic pseudospin-1/2 Dirac fermions in the deep infrared limit.At the fixed point,the fermion Green function exhibits a finite anomalous dimension,and the residue of the quasiparticle pole vanishes in a power-law fashion.Our research provides new theoretical perspectives for understanding the origin of spin-1/2 fermions in the standard model.展开更多
We investigate the behavior of non-Hermitian birefringent Dirac fermions by examining their interaction with electromagnetic fields through renormalization group analysis. Our research reveals that the interplay betwe...We investigate the behavior of non-Hermitian birefringent Dirac fermions by examining their interaction with electromagnetic fields through renormalization group analysis. Our research reveals that the interplay between non-Hermiticity and birefringence leads to distinct behaviors in two and three dimensions, where the system exhibits different fixed points and scaling properties due to dimension-dependent charge renormalization effects. In two dimensions, where the electronic charge remains unrenormalized, the system flows in the deep infrared limit from non-Hermitian birefringent spin-3/2fermions to two copies of non-Hermitian spin-1/2 Dirac fermions, demonstrating a crossover of relativistic liquid and nonrelativistic liquid. In three dimensions, dynamic screening of electromagnetic interactions modifies the logarithmic growth of Fermi velocity, leading to richer quantum corrections while maintaining similar suppression of birefringence in the infrared limit. Our findings provide theoretical insights into the emergence of Lorentz symmetry in non-Hermitian systems,laying theoretical foundations for studying low-energy behavior in other non-Hermitian models.展开更多
We demonstrate a reinforcement learning(RL)-based control framework for optimizing evaporative cooling in the preparation of strongly interacting degenerate Fermi gases of 6Li.Using a Soft Actor-Critic(SAC)algorithm,t...We demonstrate a reinforcement learning(RL)-based control framework for optimizing evaporative cooling in the preparation of strongly interacting degenerate Fermi gases of 6Li.Using a Soft Actor-Critic(SAC)algorithm,the system autonomously explores a high-dimensional parameter space to learn optimal cooling trajectories.Compared to conventional exponential ramps,our method achieves up to 130%improvement in atomic density within 0.5 second,revealing non-trivial control strategies that balance fast evaporation and thermalization.While our current optimization focuses on the evaporation stage,future integration of other cooling stages,such as gray molasses cooling,could further extend RL to the full preparation pipeline.Our result highlights the promise of RL as a general tool for closed-loop quantum control and automated calibration in complex atomic physics experiments.展开更多
We investigate distinct non-Hermitian skin effects(NHSEs)in real and Fock spaces induced by the interplay between the Hilbert space fragmentation and multiple non-Hermitian pumping channels.Using an extended Hatano–N...We investigate distinct non-Hermitian skin effects(NHSEs)in real and Fock spaces induced by the interplay between the Hilbert space fragmentation and multiple non-Hermitian pumping channels.Using an extended Hatano–Nelson model with next-nearest neighbor hopping and strong interaction as an example,we found that two fermions loaded in the lattice exhibit different real-space NHSE depending on the Hilbert space fragments to which they belong.Moreover,in the high-energy sector resulting from fragmentation,the two-particle-bound states form a one-dimensional lattice in Fock space,producing a Fock-space NHSE.At half-filling,richer patterns of Fock-space skin-like localization emerge for the different fragmented energy sectors and subsectors while realspace NHSE is suppressed by many-body effects.This study extends our understanding of the interplay between NHSE and Hilbert space fragmentation and provides detailed insights into their manifestation in interacting non-Hermitian systems.展开更多
本文通过将给定的单层周期量子图与具有循环群作用的正三边形做笛卡尔积构造了一类“三层”量子图,其中正三边形被称为连接图,得到“三层”量子图的函数空间分解和算子分解,证明了其Fermi面可约,并将结论推广到连接图为具有循环群作用的...本文通过将给定的单层周期量子图与具有循环群作用的正三边形做笛卡尔积构造了一类“三层”量子图,其中正三边形被称为连接图,得到“三层”量子图的函数空间分解和算子分解,证明了其Fermi面可约,并将结论推广到连接图为具有循环群作用的正n边形情况。 This paper constructs a class of"three-layer" quantum graphs by taking the Cartesian product of a given single-layer periodic quantum graph with an equilateral triangle (referred to as the connecting graph) endowed with a cyclic group action. The function space decomposition and operator decomposition of the resulting"three-layer" quantum graphs are derived. It is proven that their Fermi surfaces are reducible. Furthermore, the conclusions are generalized to the case where the connecting graph is a regular n-gon with a cyclic group action.展开更多
We investigate the topological phase marked by the Thouless–Kohmoto–Nightingale–Nijs（TKNN） number and the phase transitions driven by the next nearest neighbor（NNN） hopping in noncentrosymmetric cold Fermi gase...We investigate the topological phase marked by the Thouless–Kohmoto–Nightingale–Nijs（TKNN） number and the phase transitions driven by the next nearest neighbor（NNN） hopping in noncentrosymmetric cold Fermi gases, both spinsinglet pairing and spin-triplet pairing are considered. There exists a critical t＇c for the NNN hopping, at which the quantum phase transition occurs, and the system changes from an Abelian（non-Abelian） phase to a non-Abelian（Abelian） one. By numerically diagonalizing the Hamiltonian in the real space, the energy spectra with edge states for different topological phases and the Majorana zero modes are discussed. Although the spin-triplet pairing does not contribute to the gap closing and the phase diagram, it induces gapless states in the presence of a magnetic field, and the TKNN number in this region is still zero.展开更多
We demonstrate that dual dark magnetic-optical-traps(MOTs)have great importance in the two-species^(87)Rb and^(40)K mixture compared with dual bright MOTs.The dark MOT has a little improvement in the trapping of singl...We demonstrate that dual dark magnetic-optical-traps(MOTs)have great importance in the two-species^(87)Rb and^(40)K mixture compared with dual bright MOTs.The dark MOT has a little improvement in the trapping of single-species^(87)Rb or^(40)K gases compared with bright MOT.For the case of loading two-species^(87)Rb and^(40)K simultaneously,the improvement of^(40)K in the dual dark MOTs is mainly from the reduction of light-assisted collision losses.The dual dark MOTs employ a pair of conical lenses to produce the hollow beam for repump laser with high efficiency.The number and density of^(87)Rb and^(40)K atoms after evaporative cooling in the hybrid magnetic trap with dark MOT loading are compared with those in bright MOT.The atoms with large number and high density make it easier to realize the quantum degenerate of Bose-Fermi mixture.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFA1400900,2021YFA0718300,and 2021YFA1400243)the National Natural Science Foundation of China(Grant Nos.61835013,12174461,and 12234012)Space Application System of China Manned Space Program.
文摘The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced quantum electrodynamics.We used the perturbative renormalization group method to study the low-energy behavior of the system and found that it flows to a fixed point of the non-Fermi liquid composed of relativistic pseudospin-1/2 Dirac fermions in the deep infrared limit.At the fixed point,the fermion Green function exhibits a finite anomalous dimension,and the residue of the quasiparticle pole vanishes in a power-law fashion.Our research provides new theoretical perspectives for understanding the origin of spin-1/2 fermions in the standard model.
基金Project supported by the National Key Research and Development Program of China (Grants Nos. 2021YFA1400900,2021YFA0718300, and 2021YFA1400243)the National Natural Science Foundation of China (Grant Nos. 61835013,12174461, and 12234012)the Fund from the Space Application System of China Manned Space Program。
文摘We investigate the behavior of non-Hermitian birefringent Dirac fermions by examining their interaction with electromagnetic fields through renormalization group analysis. Our research reveals that the interplay between non-Hermiticity and birefringence leads to distinct behaviors in two and three dimensions, where the system exhibits different fixed points and scaling properties due to dimension-dependent charge renormalization effects. In two dimensions, where the electronic charge remains unrenormalized, the system flows in the deep infrared limit from non-Hermitian birefringent spin-3/2fermions to two copies of non-Hermitian spin-1/2 Dirac fermions, demonstrating a crossover of relativistic liquid and nonrelativistic liquid. In three dimensions, dynamic screening of electromagnetic interactions modifies the logarithmic growth of Fermi velocity, leading to richer quantum corrections while maintaining similar suppression of birefringence in the infrared limit. Our findings provide theoretical insights into the emergence of Lorentz symmetry in non-Hermitian systems,laying theoretical foundations for studying low-energy behavior in other non-Hermitian models.
基金supported by the Innovation Program for Quantum Science and Technology of China(Grant No.2024ZD0300100)the National Basic Research Program of China(Grant No.2021YFA1400900)+1 种基金Shanghai Municipal Science and Technology(Grant Nos.25TQ003,2019SHZDZX01,and 24DP2600100)the National Natural Science Foundation of China(Grant No.12304555).
文摘We demonstrate a reinforcement learning(RL)-based control framework for optimizing evaporative cooling in the preparation of strongly interacting degenerate Fermi gases of 6Li.Using a Soft Actor-Critic(SAC)algorithm,the system autonomously explores a high-dimensional parameter space to learn optimal cooling trajectories.Compared to conventional exponential ramps,our method achieves up to 130%improvement in atomic density within 0.5 second,revealing non-trivial control strategies that balance fast evaporation and thermalization.While our current optimization focuses on the evaporation stage,future integration of other cooling stages,such as gray molasses cooling,could further extend RL to the full preparation pipeline.Our result highlights the promise of RL as a general tool for closed-loop quantum control and automated calibration in complex atomic physics experiments.
基金supported by the National Natural Science Foundation of China(Grant No.12474159)the Fundamental Research Funds for the Central University,Sun Yat-sen University(Grant No.24qnpy119)the China Postdoctoral Science Foundation(Grant No.2024T171067)。
文摘We investigate distinct non-Hermitian skin effects(NHSEs)in real and Fock spaces induced by the interplay between the Hilbert space fragmentation and multiple non-Hermitian pumping channels.Using an extended Hatano–Nelson model with next-nearest neighbor hopping and strong interaction as an example,we found that two fermions loaded in the lattice exhibit different real-space NHSE depending on the Hilbert space fragments to which they belong.Moreover,in the high-energy sector resulting from fragmentation,the two-particle-bound states form a one-dimensional lattice in Fock space,producing a Fock-space NHSE.At half-filling,richer patterns of Fock-space skin-like localization emerge for the different fragmented energy sectors and subsectors while realspace NHSE is suppressed by many-body effects.This study extends our understanding of the interplay between NHSE and Hilbert space fragmentation and provides detailed insights into their manifestation in interacting non-Hermitian systems.
文摘本文通过将给定的单层周期量子图与具有循环群作用的正三边形做笛卡尔积构造了一类“三层”量子图,其中正三边形被称为连接图,得到“三层”量子图的函数空间分解和算子分解,证明了其Fermi面可约,并将结论推广到连接图为具有循环群作用的正n边形情况。 This paper constructs a class of"three-layer" quantum graphs by taking the Cartesian product of a given single-layer periodic quantum graph with an equilateral triangle (referred to as the connecting graph) endowed with a cyclic group action. The function space decomposition and operator decomposition of the resulting"three-layer" quantum graphs are derived. It is proven that their Fermi surfaces are reducible. Furthermore, the conclusions are generalized to the case where the connecting graph is a regular n-gon with a cyclic group action.
基金supported by the National Natural Science Foundation of China(Grant No.11304281)the Natural Science Foundation of Zhejiang Province,China(Grant No.LY13D060002)
文摘We investigate the topological phase marked by the Thouless–Kohmoto–Nightingale–Nijs（TKNN） number and the phase transitions driven by the next nearest neighbor（NNN） hopping in noncentrosymmetric cold Fermi gases, both spinsinglet pairing and spin-triplet pairing are considered. There exists a critical t＇c for the NNN hopping, at which the quantum phase transition occurs, and the system changes from an Abelian（non-Abelian） phase to a non-Abelian（Abelian） one. By numerically diagonalizing the Hamiltonian in the real space, the energy spectra with edge states for different topological phases and the Majorana zero modes are discussed. Although the spin-triplet pairing does not contribute to the gap closing and the phase diagram, it induces gapless states in the presence of a magnetic field, and the TKNN number in this region is still zero.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12034011,92065108,11974224,12022406,and 12004229)the National Key Research and Development Program of China(Grant No.2018YFA0307601)+1 种基金the Fund for Shanxi 1331 Project Key Subjects Constructionthe Program of Youth Sanjin Scholar。
文摘We demonstrate that dual dark magnetic-optical-traps(MOTs)have great importance in the two-species^(87)Rb and^(40)K mixture compared with dual bright MOTs.The dark MOT has a little improvement in the trapping of single-species^(87)Rb or^(40)K gases compared with bright MOT.For the case of loading two-species^(87)Rb and^(40)K simultaneously,the improvement of^(40)K in the dual dark MOTs is mainly from the reduction of light-assisted collision losses.The dual dark MOTs employ a pair of conical lenses to produce the hollow beam for repump laser with high efficiency.The number and density of^(87)Rb and^(40)K atoms after evaporative cooling in the hybrid magnetic trap with dark MOT loading are compared with those in bright MOT.The atoms with large number and high density make it easier to realize the quantum degenerate of Bose-Fermi mixture.
