Pressure induced superconductor quantum critical point in multi-band systems

TL;DR

This paper investigates how external pressure, modeled as hybridization, induces a quantum critical point in two-band superconductors, affecting their phase transition from superconducting to normal state.

Contribution

It introduces a model of a two-band superconductor with hybridization as a control parameter, analyzing the quantum phase transition using BCS approximation.

Findings

Identification of a superconducting quantum critical point driven by hybridization.

Behavior of electronic specific heat near the quantum critical point.

Shape of the critical line as hybridization approaches the critical value.

Abstract

In multi-band superconductors as inter-metallic systems and heavy fermions, external pressure can reduce the critical temperature and eventually destroy superconductivity driving these systems to the normal state. In many cases this transition is continuous and is associated with a superconducting quantum critical point (SQCP). In this work we study a two-band superconductor in the presence of hybridization V. This one-body mixing term is due to the overlap of the different wave-functions. It can be tuned by external pressure and turns out as an important control parameter to study the phase diagram and the nature of the phase transitions. We use a BCS approximation and include both inter and intra-band attractive interactions. For negligible inter-band interactions, as hybridization (pressure) increases we find a SQCP separating a superconductor from a normal state at a critical value of the hybridization Vc. We obtain the behavior of the electronic specific heat close to the SQCP and the shape of the critical line as V approaches Vc.