Pairing Correlations in the two-layer attractive Hubbard Model

TL;DR

This paper investigates pairing correlations in a two-layer attractive Hubbard model using Quantum Monte Carlo, revealing how hybridization influences superconductivity and comparing results with Bogoliubov-de Gennes approximations.

Contribution

It introduces a study of attractive multi-band systems with hybridization, highlighting the absence of a sign problem and exploring low-temperature pairing phenomena.

Findings

Pairing in the U<0 layer induces pairing in the U=0 layer at small hybridization.

Increasing hybridization V suppresses superconducting correlations in the ground state.

Quantum Monte Carlo results are complemented by Bogoliubov-de Gennes calculations.

Abstract

Studies of systems with two fermionic bands with repulsive interaction strength U have a long history, with the Periodic Anderson Model (PAM) being one of the most frequently considered Hamiltonians. In this paper, we use Quantum Monte Carlo to study analogous issues for attractive interactions. As in the Periodic Anderson Model, we focus on a case where one band is uncorrelated (U=0), and focus on the effect of hybridization V between the bands on the pairing correlations. A key difference with the PAM is that there is no sign problem, so that we are able to explore the physics of doped multi-band attractive systems at low temperatures whereas ground state properties of repulsive models can be determined only at half-filling. For small V, pairing in the U<0 layer induces pairing in the U=0 layer. At larger V the ground state of the coupled system loses its superconducting character. The Quantum Monte Carlo data are complemented by results obtained with the Bogoliubov-de Gennes approximation.