Superconductivity with s and p-symmetries in an extended Hubbard model with correlated hopping

TL;DR

This paper studies a generalized Hubbard model with correlated hopping, revealing conditions for s-wave and p-wave superconductivity, and employs Berry phases as topological order parameters to analyze the phase diagram.

Contribution

It introduces a generalized Hubbard model with occupation-dependent hopping and uses Berry phases to identify topological superconducting phases, extending previous results.

Findings

Model exhibits s-wave superconductivity under certain parameters.

Half-filling conditions lead to triplet p-wave superconductivity.

Berry phases effectively identify topological phases and phase transitions.

Abstract

We consider a generalized Hubbard model with on-site and nearest-neighbour repulsions U and V respectively, and nearest-neighbour hopping for spin up (down) which depends on the total occupation n_b of spin down (up) electrons on both sites involved. The hopping parameters are t_{AA}, t_{AB} and t_{BB} for n_b=0,1,2 respectively. We briefly summarize results which support that the model exhibits s-wave superconductivity for certain parameters and extend them by studying the Berry phases. Using a generalized Hartree-Fock(HF) BCS decoupling of the two and three-body terms, we obtain that at half filling, for t_{AB}<t_{AA}=t_{BB} and sufficiently small U and V the model leads to triplet p-wave superconductivity for a simple cubic lattice in any dimension. In one dimension, the resulting phase diagram is compared with that obtained numerically using two quantized Berry phases (topological numbers) as order parameters. While this novel method supports the previous results, there are quantitative differences.