We report the experimental realization of quantum degenerate Fermi gases of87Sr atoms under controlled 10-and dual-nuclear-spin configurations.Based on laser cooling and evaporative cooling,we achieve an ultracold Fer...We report the experimental realization of quantum degenerate Fermi gases of87Sr atoms under controlled 10-and dual-nuclear-spin configurations.Based on laser cooling and evaporative cooling,we achieve an ultracold Fermi gas of 10^(5)atoms equally distributed over 10 spin states,with a temperature of T/T_(F)=0.21.We further prepare a dual-spin gas by optically pumping atoms to the m_(F)=9/2 and m_(F)=7/2 states and observe a slightly lower T/T_(F)than that for a 10-spin gas under the same trapping condition,showing efficient evaporative cooling under a decreasing number N of spin states(N≥2)despite the increasing importance of Pauli exclusion.Given that rethermalization becomes less efficient with N approaching unity,we evaporatively cool an almost polarized gas to 130 nK.The simple and efficient preparation of ultracold Fermi gases of^(87)Sr with tunable spin configurations provides a first step towards engineering topological quantum systems.展开更多
The realization of spin-orbit-coupled ultracold gases has driven a wide range of research and is typically based on the rotating wave approximation(RWA).By neglecting the counter-rotating terms,RWA characterizes a sin...The realization of spin-orbit-coupled ultracold gases has driven a wide range of research and is typically based on the rotating wave approximation(RWA).By neglecting the counter-rotating terms,RWA characterizes a single near-resonant spin-orbit(SO)coupling in a two-level system.Here,we propose and experimentally realize a new scheme for achieving a pair of two-dimensional(2D)SO couplings for ultracold fermions beyond RWA.This work not only realizes the first anomalous Floquet topological Fermi gas beyond RWA,but also significantly improves the lifetime of the 2D-SO-coupled Fermi gas.Based on pump-probe quench measurements,we observe a deterministic phase relation between two sets of SO couplings,which is characteristic of our beyond-RWA scheme and enables the two SO couplings to be simultaneously tuned to the optimum 2D configurations.We observe intriguing band topology by measuring two-ring band-inversion surfaces,quantitatively consistent with a Floquet topological Fermi gas in the regime of high Chern numbers.Our study can open an avenue to explore exotic SO physics and anomalous topological states based on long-lived SO-coupled ultracold fermions.展开更多
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0300901 and 2018YFA0305601the National Natural Science Foundation of China under Grant No 11874073the International Center for Quantum Materials of Peking University
文摘We report the experimental realization of quantum degenerate Fermi gases of87Sr atoms under controlled 10-and dual-nuclear-spin configurations.Based on laser cooling and evaporative cooling,we achieve an ultracold Fermi gas of 10^(5)atoms equally distributed over 10 spin states,with a temperature of T/T_(F)=0.21.We further prepare a dual-spin gas by optically pumping atoms to the m_(F)=9/2 and m_(F)=7/2 states and observe a slightly lower T/T_(F)than that for a 10-spin gas under the same trapping condition,showing efficient evaporative cooling under a decreasing number N of spin states(N≥2)despite the increasing importance of Pauli exclusion.Given that rethermalization becomes less efficient with N approaching unity,we evaporatively cool an almost polarized gas to 130 nK.The simple and efficient preparation of ultracold Fermi gases of^(87)Sr with tunable spin configurations provides a first step towards engineering topological quantum systems.
基金supported by the Chinese Academy of Sciences Strategic Priority Research Program(XDB35020100)the National Key Research and Development Program of China(2021YFA1400900 and 2018YFA0305601)+3 种基金the National Natural Science Foundation of China(11874073,12304564,11825401,12204187,12261160368)the Open Project of Shenzhen Institute of Quantum Science and Engineering(SIQSE202003)the Hefei National Laboratorythe Scientific and Technological Innovation 2030 Key Program of Quantum Communication and Quantum Computing(2021ZD0301903 and 2021ZD0302000)。
文摘The realization of spin-orbit-coupled ultracold gases has driven a wide range of research and is typically based on the rotating wave approximation(RWA).By neglecting the counter-rotating terms,RWA characterizes a single near-resonant spin-orbit(SO)coupling in a two-level system.Here,we propose and experimentally realize a new scheme for achieving a pair of two-dimensional(2D)SO couplings for ultracold fermions beyond RWA.This work not only realizes the first anomalous Floquet topological Fermi gas beyond RWA,but also significantly improves the lifetime of the 2D-SO-coupled Fermi gas.Based on pump-probe quench measurements,we observe a deterministic phase relation between two sets of SO couplings,which is characteristic of our beyond-RWA scheme and enables the two SO couplings to be simultaneously tuned to the optimum 2D configurations.We observe intriguing band topology by measuring two-ring band-inversion surfaces,quantitatively consistent with a Floquet topological Fermi gas in the regime of high Chern numbers.Our study can open an avenue to explore exotic SO physics and anomalous topological states based on long-lived SO-coupled ultracold fermions.
