BCS-BEC crossover in a random external potential

TL;DR

This paper studies how disorder affects the ground state of a superfluid Fermi gas across the BCS-BEC crossover, revealing nonmonotonic behavior and the breakdown of Anderson's theorem in certain regimes.

Contribution

It provides new insights into the impact of weak disorder on superfluid properties across the BCS-BEC crossover, highlighting nonmonotonic trends and the limits of Anderson's theorem.

Findings

Condensate depletion and normal fluid density show nonmonotonic behavior near unitarity.

Superfluid order parameter is increasingly affected by disorder away from weak coupling.

Weak disorder can minimize condensate depletion near unitarity.

Abstract

We investigate the ground state properties of a disordered superfluid Fermi gas across the BCS-BEC (Bose Einstein condensate) crossover. We show that, for weak disorder, both the depletion of the condensate fraction of pairs and the normal fluid density exhibit a nonmonotonic behavior as a function of the interaction parameter $1/k_Fa$, reaching their minimum value near unitarity. We find that, moving away from the weak coupling BCS regime, Anderson's theorem ceases to apply and the superfluid order parameter is more and more affected by the random potential.