Optical response of graphene under strain

Abstract

Strain has been known to modify the electric and optical properties of graphene. This phenomenon has attracted interest to modifying graphene properties using specific forms of strains (known as strain-engineering), and measuring strain in graphene. In this thesis, I present a calculation of the optical properties of strained graphene, where the effects of strain can be seen in the optical conductivity and thus the reflectivity of graphene.

To do this, I use the tight-binding model to obtain the Dirac Hamiltonian of the charge carriers in graphene. Then I deduce the effects of in-plane strain as a pseudo-magnetic field potential and use this result to add strain as a perturbation to the Hamiltonian of pristine graphene.

Using the perturbed Hamiltonian, I calculate the optical conductivity of graphene for a specific strain field with a $y$-component that is periodic in $x$. I obtain the optical conductivity numerically for different amplitudes of the strain, and use them to find the reflectivity.

The results indicate that the effects of strain on reflectivity can be measured experimentally, and that such measurements can reveal information about the amplitude and period of the strain.