Polarization Dependence of Raman Spectra in Strained Graphene

TL;DR

This paper theoretically investigates how the polarization of Raman spectra bands in strained graphene varies at bulk and edges, revealing different selection rules and the influence of edges on pseudospin and valleyspin behaviors.

Contribution

It introduces a theoretical analysis of polarization dependence in Raman spectra of graphene, highlighting the role of edge constraints on electronic properties.

Findings

2D band intensity peaks when polarization is parallel at bulk

D band shows no polarization dependence at bulk

Edge effects influence pseudospin and valleyspin interactions

Abstract

The polarization dependences of the G, D, and 2D (G$'$) bands in Raman spectra at graphene bulk and edge are examined theoretically. The 2D and D bands have different selection rules at bulk and edge. At bulk, the 2D band intensity is maximum when the polarization of the scattered light is parallel to that of incident light, whereas the D band intensity does not have a polarization dependence. At edge, the 2D and D bands exhibit a selection rule similar to that of the G band proposed in a previous paper. We suggest that a constraint equation on the axial velocity caused by the graphene edge is essential for the dependence of the G band on the crystallographic orientation observed in the bulk of strained graphene. This is indicative of that the pseudospin and valleyspin in the bulk of graphene can not be completely free from the effect of surrounding edge. The status of the experiments on the G and D bands at the graphene edge is mentioned.