# Strong coupling effects on specific heat in the BCS-BEC crossover

## TL;DR

This paper theoretically examines how strong-coupling effects influence the specific heat in a superfluid Fermi gas across the BCS-BEC crossover, highlighting the role of Goldstone modes in low-temperature behavior.

## Contribution

It introduces a calculation of specific heat considering superfluid fluctuations at unitarity, revealing the dominance of Goldstone modes at low temperatures.

## Key findings

- Low-temperature specific heat exhibits T^3 behavior.
- Goldstone mode fluctuations dominate low-energy excitations.
- Results enhance understanding of pairing fluctuations in superfluid Fermi gases.

## Abstract

We theoretically investigate strong-coupling effects on specific heat at constant volume $C_{\rm V}$ in a superfluid Fermi gas with a tunable interaction associated with Feshbach resonance. Including fluctuations of the superfluid order parameter within the strong-coupling theory developed by Nozi\`eres and Schmitt-Rink, we calculate the temperature dependence of $C_{\rm V}$ at the unitarity limit in the superfluid phase. We show that, in the low temperature region, $T^3$-behavior is shown in the temperature dependence of $C_{\rm V}$. This result indicates that the low-lying excitations are dominated by the gapless Goldstone mode, associated with the phase fluctuations of the superfluid order parameter. Since the Goldstone mode is one of the most fundamental phenomena in the Fermionic superfluidity, our results are useful for further understanding how the pairing fluctuations affects physical properties in the BCS-BEC crossover physics below the superfluid transition temperature.