Trigonal warping and anisotropic band splitting in monolayer graphene due to Rashba spin-orbit coupling

TL;DR

This paper investigates how Rashba spin-orbit coupling affects the electronic band structure of monolayer graphene, revealing trigonal warping, Fermi surface breakup, and implications for conductivity and spin polarization, aligning with experimental data.

Contribution

It demonstrates that strong Rashba spin-orbit coupling causes trigonal warping and Fermi surface breakup in monolayer graphene, a novel insight into its electronic properties.

Findings

Trigonal warping occurs when Rashba coupling exceeds intrinsic coupling.

Fermi surface breaks into separate parts below Lifshitz energy.

Predicted effects match recent experimental observations.

Abstract

We study the electronic band structure of monolayer graphene when Rashba spin-orbit coupling is present. We show that if the Rashba spin-orbit coupling is stronger than the intrinsic spin-orbit coupling, the low energy bands undergo trigonal-warping deformation and that for energies smaller than the Lifshitz energy, the Fermi circle breaks up into separate parts. The effect is very similar to what happens in bilayer graphene at low energies. We discuss the possible experimental implications, such as threefold increase of the minimal conductivity for low electron densities, the wavenumber dependence of the band splitting and the spin polarization structure. Our theoretical predictions are in agreement with recent experimental results.