Speed of sound of a spin balanced Fermi gas with s- and d-wave pairings across the BCS-BEC evolution

TL;DR

This paper investigates the behavior of the speed of sound in a spin-balanced Fermi gas with s- and d-wave pairings across the BCS-BEC crossover, finding it to be smooth and analytic at the chemical potential vanishing point, contrary to previous claims.

Contribution

The study provides numerical evidence that the speed of sound remains analytic across the BCS-BEC transition in 2D Fermi gases with s- and d-wave pairings, challenging prior theoretical predictions.

Findings

Speed of sound is smooth and analytic at the chemical potential vanishing point.

Contradicts previous claims of nonanalytic behavior in d-wave pairing systems.

Supports the idea of a continuous BCS-BEC crossover in these systems.

Abstract

The authors of a recent paper (PRA \textbf{87}, 013613 (2013)) argued that in fermionic systems with d-wave pairing the speed of sound is nonanalytic across the BCS-BEC crossover at the point where the chemical potential vanishes, regardless of the specific details of the interaction potential. On the contrary, the numerical results reported here suggest that the speed of sound across the BCS-BEC evolution of atomic Fermi gases with s- and d-wave pairings in two-dimensional square lattices is a smooth analytic function at the vanishing chemical potential.