Pairing in graphene: A quantum Monte Carlo study

TL;DR

This study uses quantum Monte Carlo simulations to investigate electron pairing in graphene, revealing that d+id pairing dominates near half filling but diminishes with system size and Coulomb interactions, and that nearest-neighbor interactions suppress d+id pairing.

Contribution

It provides a systematic quantum Monte Carlo analysis of pairing symmetries in the Hubbard model on a honeycomb lattice, highlighting the effects of interactions on pairing correlations.

Findings

d+id pairing dominates near half filling

Long-range d+id pairing correlation decreases with system size

Nearest-neighbor interactions suppress d+id pairing

Abstract

To address the issue of electron correlation driven superconductivity in graphene, we perform a systematic quantum Monte Carlo study of the pairing correlation in the t-U-V Hubbard model on a honeycomb lattice. For V=0 and close to half filling, we find that pairing with d+id symmetry dominates pairing with extended-s symmetry. However, as the system size or the on-site Coulomb interaction increases, the long-range part of the d+id pairing correlation decreases and tends to vanish in the thermodynamic limit. An inclusion of nearest-neighbor interaction V, either repulsive or attractive, has a small effect on the extended-s pairing correlation, but strongly suppresses the d+id pairing correlation.