Spin-density-wave instability in graphene doped near the van Hove singularity

TL;DR

This paper investigates the potential for spin-density-wave (SDW) formation in highly doped graphene near the van Hove singularity, revealing a preference for SDW over ferromagnetism under certain conditions.

Contribution

It introduces a theoretical analysis of SDW instability in doped graphene using the Hubbard model and field theory, highlighting the conditions favoring SDW with a triangular geometry.

Findings

SDW with triangular geometry is favored above a critical interaction strength

The critical Hubbard parameter U_c(T) depends on temperature and doping levels

Results suggest experimental verification via ARPES or neutron scattering

Abstract

We study the instability of the metallic state towards the formation of a new ground state in graphene doped near the van Hove singularity. The system is described by the Hubbard model and a field theoretical approach is used to calculate the charge and spin susceptibility. We find that for repulsive interactions, within the random phase approximation, there is a competition between ferromagnetism and spin-density wave (SDW). It turns out that a SDW with a triangular geometry is more favorable when the Hubbard parameter is above the critical value U_c(T), which depends on the temperature T, even if there are small variations in the doping. Our results can be verified by ARPES or neutron scattering experiments in highly doped graphene.