自旋轨道耦合作用下超冷费米气体中的BCS-BEC渡越及量子相变

In this work, we study the BCS-BEC crossover and quantum phase transitions in a Fermi gas under Rashba spin-orbit coupling close to a Feshbach resonance. By adopting a two-channel model, we take into account of the closed channel molecules, and show that combined with spin-orbit coupling, a finite background scattering in the open channel can lead to two branches of solution for both the two-body and the many-body ground states. The branching of the two-body bound state solutions originate from the avoided crossing between bound states from the open and the closed channels, respectively. Unlike the case without spin-orbit coupling, we identify a quantum phase transition in the upper branch regardless of the sign of the background scattering length. For systems with negative background scattering length in particular, we show that the bound state in the open channel, and hence the quantum phase transition in the upper branch, are induced by spin-orbit coupling. ?????