Fluctuation Effects on the Transport Properties of Unitary Fermi Gases

TL;DR

This paper explores how fluctuations near the superfluid transition temperature affect transport properties in unitary Fermi gases, extending theories from superconductors to ultracold gases and predicting non-monotonic paraconductivity behavior.

Contribution

It generalizes fluctuation effects on transport from BCS superconductors to the unitary Fermi gas regime using the time-dependent Ginzburg-Landau formalism.

Findings

Residual resistivity increases near unitarity, matching experiments

Paraconductivity shows non-monotonic temperature dependence

Results are testable with mesoscopic transport experiments

Abstract

In this letter, we investigate the fluctuation effects on the transport properties of unitary Fermi gases in the vicinity of the superfluid transition temperature $T_c$. Based on the time-dependent Ginzburg-Landau formalism of the BEC-BCS crossover, we investigate both the residual resistivity below $T_c$ induced by phase slips and the paraconductivity above $T_c$ due to pair fluctuations. These two effects have been well studied in the weak coupling BCS superconductor, and here we generalize them to the unitary regime of ultracold Fermi gases. We find that while the residual resistivity below $T_c$ increases as one approaches the unitary limit, consistent with recent experiments, the paraconductivity exhibits non-monotonic behavior. Our results can be verified with the recently developed transport apparatus using mesoscopic channels.