Normal-Superfluid Interface for Polarized Fermion Gases

TL;DR

This paper investigates the thermal properties of the interface between superfluid and normal phases in polarized fermion gases, revealing that energy transfer is suppressed at low temperatures due to the superfluid gap, leading to a temperature difference.

Contribution

It provides a quantitative analysis of the N-SF interface using the Hartree-Fock-Bogoliubov-de Gennes formalism, highlighting the exponential suppression of thermal conductivity at low temperatures.

Findings

Thermal conductivity across the interface is exponentially small at low temperatures.

A temperature difference can develop between N and SF phases due to energy transfer blocking.

The analysis includes cases with unequal masses at the interface.

Abstract

Recent experiments on imbalanced fermion gases have proved the existence of a sharp interface between a superfluid and a normal phase. We show that, at the lowest experimental temperatures, a temperature difference between N and SF phase can appear as a consequence of the blocking of energy transfer across the interface. Such blocking is a consequence of the existence of a SF gap, which causes low-energy normal particles to be reflected from the N-SF interface. Our quantitative analysis is based on the Hartree-Fock-Bogoliubov-de Gennes formalism, which allows us to give analytical expressions for the thermodynamic properties and characterize the possible interface scattering regimes, including the case of unequal masses. Our central result is that the thermal conductivity is exponentially small at the lowest experimental temperatures.