Title: Dimensionality effect on exceptional fermionic superfluidity with spin-dependent asymmetric hopping Show Chinese title

Title: 自旋依赖的非对称跃迁对异常费米子超流性的影响

Abstract: Non-Hermitian (NH) quantum systems host exceptional points (EPs), where eigenstates and eigenvalues coalesce, leading to unconventional many-body phenomena absent in Hermitian systems. While NH fermionic systems with complex interactions exhibit superfluid (SF) breakdown with EPs, spin-dependent asymmetric hopping can stabilize a NH superfluid (NH-SF) that coexists with EPs. In this work, we investigate the quasi-one-dimensional NH attractive Fermi-Hubbard model by using NH BCS theory. We demonstrate that, when the system is regarded as weakly-coupled chains, the exceptional SF phase becomes unstable and metastable (exceptional) SF state appears between the stable SF and normal states. In the one-dimensional limit, the exceptional SF disappear entirely and EPs only appear on the phase boundary between the normal and SF states. These results reveal how dimensional crossover governs the stability of the exceptional SF, providing the insights into the interplay between dimensionality and dissipation, with potential relevance for experimental implications in ultracold atoms. Show Chinese abstract

Abstract: 非厄米（NH）量子系统包含异常点（EPs），在这些点上本征态和本征值合并，导致在厄米系统中不存在的非常规多体现象。 虽然具有复数相互作用的NH费米系统在EPs处表现出超流（SF）破坏，但自旋依赖的不对称跳跃可以稳定一个与EPs共存的NH超流（NH-SF）。 在本工作中，我们通过使用NH BCS理论研究了一维准一维的NH吸引费米-哈伯德模型。 我们证明，当系统被视为弱耦合链时，异常SF相变得不稳定，并且在稳定SF和正常态之间出现亚稳（异常）SF态。 在一维极限下，异常SF完全消失，EPs仅出现在正常态和SF态之间的相变边界上。 这些结果揭示了维度交叉如何支配异常SF的稳定性，为理解维度和耗散之间的相互作用提供了见解，对超冷原子的实验应用具有潜在的相关性。