Pressure induced BEC-BCS crossover in multi-band superconductors

TL;DR

This paper investigates how pressure can induce a BEC-BCS crossover in multi-band superconductors by modifying electronic structures and hybridization, revealing a pressure-driven quantum critical point.

Contribution

It introduces a model for pressure-dependent hybridization in multi-band systems and demonstrates pressure can induce a BCS-BEC crossover even at moderate interactions.

Findings

Pressure can induce a superconductor quantum critical point.

Hybridization under pressure can cause a BCS-BEC crossover.

The symmetry of the order parameter influences the results.

Abstract

Superconductivity in strongly correlated systems is a remarkable phenomenon that attracts a huge interest. The study of this problem is relevant for materials as the high $T_c$ oxides, pnictides and heavy fermions. These systems also have in common the existence of electrons of several orbitals that coexist at a common Fermi-surface. In this paper we study the effect of pressure, chemical or applied on multi-band superconductivity. Pressure varies the atomic distances and consequently the overlap of the wave-functions in the crystal. This rearranges the electronic structure that we model including a pressure dependent hybridization between the bands. We consider the case of two-dimensional systems in a square lattice with inverted bands. We study the conditions for obtaining a pressure induced superconductor quantum critical point and show that hybridization, i.e., pressure can induce a BCS-BEC crossover in multi-band systems even for moderate interactions. We briefly discuss the influence of the symmetry of the order parameter in the results.