Finite-Momentum Dimer Bound State in Spin-Orbit Coupled Fermi Gas

TL;DR

This paper explores how spin-orbit coupling in a Fermi gas leads to finite-momentum dimer bound states, revealing broken Galilean invariance and implications for many-body physics.

Contribution

It demonstrates the existence of finite-momentum dimer states induced by spin-orbit coupling and Zeeman fields, highlighting a novel effect of broken Galilean invariance in such systems.

Findings

Finite-momentum dimer bound states exist under certain conditions.

Broken Galilean invariance due to spin-orbit coupling.

Implications for many-body properties of Fermi gases.

Abstract

We investigate the two-body properties of a spin-1/2 Fermi gas subject to a spin-orbit coupling induced by laser fields. When an attractive s-wave interaction between unlike spins is present, the system may form a dimer bound state. Surprisingly, in the presence of a Zeeman field along the direction of the spin-orbit coupling, the bound state obtains finite center-of-mass mechanical momentum, whereas under the same condition but in the absence of the two-body interaction, the system has zero total momentum. This unusual result can be regarded as a consequence of the broken Galilean invariance by the spin-orbit coupling. Such a finite-momentum bound state will have profound effects on the many-body properties of the system.