Anomalous specific heat jump in a two-component ultracold Fermi gas

TL;DR

This paper investigates the thermodynamics of a spin-imbalanced Fermi gas in the BCS limit, revealing an anomalous specific heat jump and phase transition phenomena that could be experimentally observed.

Contribution

It introduces the analysis of anomalous specific heat behavior and unpairing phase transition in a two-component ultracold Fermi gas with population imbalance.

Findings

Anomalous enhancement of entropy and specific heat above unpaired state values

Identification of a second specific heat jump at the unpairing transition

Metastable superfluid states possible under adiabatic cooling

Abstract

The thermodynamic functions of a Fermi gas with spin population imbalance are studied in the temperature-asymmetry plane in the BCS limit. The low temperature domain is characterized by anomalous enhancement of the entropy and the specific heat above their values in the unpaired state, decrease of the gap and eventual unpairing phase transition as the temperature is lowered. The unpairing phase transition induces a second jump in the specific heat, which can be measured in calorimetric experiments. While the superfluid is unstable against a supercurrent carrying state, it may sustain a metastable state if cooled adiabatically down from the stable high-temperature domain. In the latter domain the temperature dependence of the gap and related functions is analogous to the predictions of the BCS theory.