Competing pairing channels in the doped honeycomb lattice Hubbard model

TL;DR

This study uses large-scale DCA calculations to explore the evolution of pairing symmetries in the doped honeycomb lattice Hubbard model, revealing a transition from $d+id$ singlet to $p$-wave triplet pairing with increasing interaction strength.

Contribution

It provides systematic, large-scale computational evidence for the doping- and interaction-dependent competition between different pairing symmetries in the Hubbard model.

Findings

$d+id$ pairing dominates near VHS at weak coupling

Enhanced $p$-wave triplet pairing at stronger interactions

Systematic evolution of pairing symmetry with cluster size

Abstract

Proposals for superconductivity emerging from correlated electrons in the doped Hubbard model on the honeycomb lattice range from chiral $d+id$ singlet to $p+ip$ triplet pairing, depending on the considered range of doping and interaction strength, as well as the approach used to analyze the pairing instabilities. Here, we consider these scenarios using large-scale dynamic cluster approximation (DCA) calculations to examine the evolution in the leading pairing symmetry from weak to intermediate coupling strength. These calculations focus on doping levels around the van Hove singularity (VHS) and are performed using DCA simulations with an interaction-expansion continuous-time quantum Monte Carlo cluster solver. We calculated explicitly the temperature dependence of different uniform superconducting pairing susceptibilities and found a consistent picture emerging upon gradually increasing the cluster size: while at weak coupling the $d+id$ singlet pairing dominates close to the VHS filling, an enhanced tendency towards $p$-wave triplet pairing upon further increasing the interaction strength is observed. The relevance of these systematic results for existing proposals and ongoing pursuits of odd-parity topological superconductivity are also discussed.