Monolayer graphene panorama, Majorana modes and Longitudinal conductivity

TL;DR

This paper explores the theoretical emergence of Majorana-like modes in monolayer graphene with specific perturbations and predicts a nearly universal longitudinal conductivity near 2.018 e^2/h at room temperature.

Contribution

It introduces a model where valley-mixing and spin-degeneracy lifting lead to Majorana modes and calculates the resulting longitudinal conductivity using the Kubo formula.

Findings

Identification of eight Majorana-like modes near Dirac points.

Prediction of nearly universal room temperature conductivity (~2.018 e^2/h).

Qualitative agreement with experimental finite conductivity in graphene.

Abstract

We take a wide-angle view of the problem of monolayer graphene where the valley-mixing and the spin-degeneracy lifting are assumed to be possible by wedging in the requisite ingredients, viz. the atomically sharp scatterers and the strong Rashba coupling dominating over the intrinsic spin-orbit coupling. This leads to eight Majorana-like modes (quasi-particles which are self-conjugate) close to the experimentally inaccessible Dirac points. Using Kubo formula we also show that the semi-classical diffusive (longitudinal) conductivity is nearly (2.018 e2/h) at room temperature for the disordered system. Though this is an overestimation, we have been, never-the-less, able to qualitatively capture the fact that the room temperature conductivity of graphene is finite and the contribution to the conductivity arises from the momentum very close to the Dirac points.