Asymmetric superconductivity in metallic systems

TL;DR

This paper investigates asymmetric superconductivity in two-band metallic systems with transmutable fermions, revealing various phase transitions and instabilities influenced by hybridization and inter/intra-band interactions.

Contribution

It introduces a comprehensive analysis of superconductivity in systems with transmutable fermions, highlighting the effects of hybridization and multiple interactions on phase transitions.

Findings

First order normal-superconductor transition with gapless excitations

Continuous transition at a quantum critical point for intra-band interactions

Presence of metastable phases with unique excitation spectra

Abstract

Different types of superfluid ground states have been investigated in systems of two species of fermions with Fermi surfaces that do not match. This study is relevant for cold atomic systems, condensed matter physics and quark matter. In this paper we consider this problem in the case the fermionic quasi-particles can transmute into one another and only their total number is conserved. We use a BCS approximation to study superconductivity in two-band metallic systems with inter and intra-band interactions. Tuning the hybridization between the bands varies the mismatch of the Fermi surfaces and produces different instabilities. For inter-band attractive interactions we find a first order normal-superconductor and a homogeneous metastable phase with gapless excitations. In the case of intra-band interactions, the transition from the superconductor to the normal state as hybridization increases is continuous and associated with a quantum critical point. The case when both interactions are present is also considered.