Unconventional pairings of spin-orbit coupled attractive degenerate Fermi gas in a one dimensional optical lattice

摘要

Understanding novel pairings in attractive degenerate Fermi gases is crucialfor exploring rich superfluid physics. In this report, we reveal unconventionalpairings induced by spin-orbit coupling (SOC) in a one-dimensional opticallattice, using a state-of-the-art density-matrix renormalization group method.When both bands are partially occupied, we find a strong competition betweenthe interband Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) and intrabandBardeen-Cooper-Schrieffer (BCS) pairings. In particular, for the weak andmoderate SOC strengths, these two pairings can coexist, giving rise to a newphase called the FFLO-BCS phase, which exhibits a unique three-peak structurein pairing momentum distribution. For the strong SOC strength, the intrabandBCS pairing always dominates in the whole parameter regime, including the halffilling. We figure out the whole phase diagrams as functions of filling factor,SOC strength, and Zeeman field. Our results are qualitatively different fromrecent mean-field predictions. Finally, we address that our predictions couldbe observed in a weaker trapped potential.