First Order Superfluid to Bose Metal Transition in Systems with Resonant Pairing

TL;DR

This paper investigates a first order phase transition from a superfluid to a Bose metal in systems with resonant pairing, characterized by a change in the fermionic spectrum and collective modes as the exchange coupling increases.

Contribution

It identifies and characterizes a first order transition driven by exchange coupling in resonant superfluid systems, revealing a transition from a gapped superfluid to an uncorrelated bosonic liquid.

Findings

Superfluid phase exhibits a fermionic gap and collective sound modes.

Transition occurs at a critical coupling g_c, beyond which the phase becomes a Bose metal.

The Bose metal phase has a quadratic q spectrum, indicating uncorrelated bosonic behavior.

Abstract

Systems showing resonant superfluidity, driven by an exchange coupling of strength $g$ between uncorrelated pairs of itinerant fermions and tightly bound ones, undergo a first order phase transition as $g$ increases beyond some critical value $g_c$. The superfluid phase for $g \leq g_c$ is characterized by a gap in the fermionic single particle spectrum and an acoustic sound-wave like collective mode of the bosonic resonating fermion pairs inside this gap. For $g>g_c$ this state gives way to a phase uncorrelated bosonic liquid with a $q^2$ spectrum.