The Role of Interaction in the Pairing of Two Spin-orbit Coupled Fermions

TL;DR

This paper explores how repulsive s-wave interactions influence the pairing of two spin-orbit coupled fermions, revealing complex ground state behaviors and transitions relevant for exotic superfluid phases.

Contribution

It provides an analytical and exact solution to the two-body problem with spin-orbit coupling, highlighting the importance of high-energy states and interaction tuning.

Findings

High-energy states influence binding energy at weak spin-orbit coupling.

Tuning interactions causes zigzag ground state momentum and metastable state transitions.

Results applicable even when spin-orbit coupling significantly alters the density of states.

Abstract

We investigate the role of a repulsive s-wave interaction in the two-body problem in the presence of spin orbit couplings, motivated by current interests in exploring exotic superfluid phases in spin-orbit coupled Fermi gases. For weak spin orbit coupling where the density of states is not significantly altered, we analytically show that the high-energy states become more important in determining the binding energy when the interaction strength decreases. Consequently, tuning the interaction gives rise to a rich ground state behavior, including a zigzag of the ground state momentum or inducing transitions among the meta-stable states. By exactly solving the two-body problem for a spin-orbit coupled Fermi mixture, we demonstrate that our analysis can also apply to the case when the density of states is significantly modified by the spin-orbit coupling. Our findings pave the way for understanding and controlling the paring of fermions in the presence of spin orbit couplings.