BCS-BEC crossover in three-dimensional Fermi gases with spherical spin-orbit coupling

TL;DR

This paper provides a comprehensive theoretical analysis of the BCS-BEC crossover in three-dimensional Fermi gases with spherical spin-orbit coupling, revealing the emergence of rashbon bound states and universal behaviors at strong coupling.

Contribution

It introduces a systematic theoretical framework for understanding the BCS-BEC crossover with spherical spin-orbit coupling, including the properties of rashbon states and collective excitations.

Findings

Identification of rashbon bound states with non-trivial effective mass at large spin-orbit coupling

Analytical results showing universal behaviors in physical quantities at strong coupling

Predictions that can be tested in future cold Fermi gas experiments

Abstract

We present a systematic theoretical study of the BCS-BEC crossover problem in three-dimensional atomic Fermi gases at zero temperature with a spherical spin-orbit coupling which can be generated by a synthetic non-Abelian gauge field coupled to neutral fermions. Our investigations are based on the path integral formalism which is a powerful theoretical scheme for the study of the properties of the bound state, the superfluid ground state, and the collective excitations in the BCS-BEC crossover. At large spin-orbit coupling, the system enters the BEC state of a novel type of bound state (referred to as rashbon) which possesses a non-trivial effective mass. Analytical results and interesting universal behaviors for various physical quantities at large spin-orbit coupling are obtained. Our theoretical predictions can be tested in future experiments of cold Fermi gases with three-dimensional spherical spin-orbit coupling.