Pairing and chiral spin density wave instabilities on the honeycomb lattice: a comparative quantum Monte Carlo study

TL;DR

This study uses quantum Monte Carlo simulations to analyze pairing tendencies and spin density wave instabilities in the Hubbard model on a honeycomb lattice, revealing dominant singlet d+id-wave pairing and the relevance of chiral SDW order at specific doping levels.

Contribution

It provides a comparative quantum Monte Carlo analysis of pairing and SDW instabilities on the honeycomb lattice, focusing on weak coupling regimes and doping effects.

Findings

Singlet d+id-wave pairing is dominant at and away from VHS.

Chiral SDW order is relevant at VHS but diminishes with doping.

Weak coupling regime analysis due to sign problem limitations.

Abstract

Using finite-temperature determinantal quantum Monte Carlo calculations, we re-examine the pairing susceptibilities in the Hubbard model on the honeycomb lattice, focusing on doping levels onto and away from the van Hove singularity (VHS) filling. For this purpose, electronic densities of $0.75$ (at the hole-doping VHS) and $0.4$ (well below the VHS) are considered in detail, where due to a severe sign problem at strong coupling strengths, we focus on the weak interaction region of the Hubbard model Hamiltonian. From analyzing the temperature dependence of pairing susceptibilities in various symmetry channels, we find the singlet $d$+$id$-wave to be the dominant pairing channel both at and away from the VHS filling. We furthermore investigate the electronic susceptibility to a specific chiral spin density wave (SDW) order, which we find to be similarly relevant at the VHS, while it extenuates upon doping away from the VHS filling.