Short-range correlations in dilute atomic Fermi gases with spin-orbit coupling

TL;DR

This paper investigates how spin-orbit coupling influences short-range correlations in dilute atomic Fermi gases, revealing that such coupling enhances correlations at both high and zero temperatures, with potential experimental detection.

Contribution

It provides the first detailed analysis of the impact of spin-orbit coupling on short-range correlations in Fermi gases, including derivations of virial expansion and bound state properties.

Findings

Correlation strength increases with spin-orbit coupling at high temperature.

Presence of zero-momentum two-body bound states with symmetric spin-orbit coupling.

Enhanced short-range correlations due to spin-orbit coupling at zero temperature.

Abstract

We study the short-range correlation strength of three dimensional spin half dilute atomic Fermi gases with spin-orbit coupling. The interatomic interaction is modeled by the contact pseudopotential. In the high temperature limit, we derive the expression for the second order virial expansion of the thermodynamic potential via the ladder diagrams. We further evaluate the second order virial expansion in the limit that the spin-orbit coupling constants are small, and find that the correlation strength between the fermions increases as the forth power of the spin-orbit coupling constants. At zero temperature, we consider the cases in which there are symmetric spin-orbit couplings in two or three directions. In such cases, there is always a two-body bound state of zero net momentum. In the limit that the average interparticle distance is much larger than the dimension of the two-body bound state, the system primarily consists of condensed bosonic molecules that fermions pair to form; we find that the correlation strength also becomes bigger compared to that in the absence of spin-orbit coupling. Our results indicate that generic spin-orbit coupling enhances the short-range correlations of the Fermi gases. Measurement of such enhancement by photoassociation experiment is also discussed.