Enhanced fermion pairing and superfluidity by an imaginary magnetic field

We show that an imaginary magnetic field(IMF), which can be generated in non-Hermitian systems with spin-dependent dissipations, can greatly enhance the s-wave pairing and superfluidity of spin-1/2 fermions, in distinct contrast to the effect of a real magnetic field. The enhancement can be attributed to the increased coupling constant in low-energy space and the reduced spin gap in forming singlet pairs. We have demonstrated this effect in a number of different fermion systems with and without spin-orbit coupling, using both the two-body exact solution and many-body mean-field theory. Our results suggest an alternative route towards strong fermion superfluid with high superfluid transition temperature.Comment: 5 pages, 4 figures; version accepted by iScienc

Engineering Non-Hermitian Skin Effect with Band Topology in Ultracold Gases

Non-Hermitian skin effect(NHSE) describes a unique non-Hermitian phenomenon that all eigen-modes are localized near the boundary, and has profound impact on a wide range of bulk properties. In particular, topological systems with NHSE have stimulated extensive research interests recently, given the fresh theoretical and experimental challenges therein. Here we propose a readily implementable scheme for achieving NHSE with band topology in ultracold gases. Specifically, the scheme realizes the one-dimensional optical Raman lattice with two types of spin-orbit coupling (SOC) and an additional laser-induced dissipation. By tuning the dissipation and the SOC strengths, NHSE and band topology can be individually controlled such that they can coexist in a considerable parameter regime. To identify the topological phase in the presence of NHSE, we have restored the bulk-boundary correspondence by invoking the non-Bloch band theory, and discussed the dynamic signals for detection. Our work serves as a guideline for engineering topological lattices with NHSE in the highly tunable environment of cold atoms, paving the way for future studies of exotic non-Hermitian physics in a genuine quantum many-body setting.Comment: 9+4 pages, 5+6 figure