Magnetization of Graphene with Circularly Polarized Light

Abstract

In this thesis, the effect of circularly polarized light on a graphene sheet is explored. The fundamental question that we try to answer in this work is whether circularly polarized light is able to induce a DC magnetization in a sheet of graphene. We also consider whether that magnetization can be related to important structural constants and if the form it takes can be connected to the Inverse Faraday Effect. We first describe the basics of graphene and its lattice structure and energy dispersion. We then discuss some of the literature regarding optomagnetics and the Inverse Faraday Effect, including Pitaevskii’s paper which uses the Maxwell-Abraham stress tensor to predict static magnetization in a dispersive, transparent medium. In the theoretical analysis section, we use a quantum mechanical approach to calculate modified wavefunctions for graphene using a modified Hamiltonian. After obtaining the new wavefunctions, we apply these wavefunctions in the context of a quantum mechanical expectation value to find the magnetization. We find an analytical expression for the DC magnetization which includes very important structural constants as we expected and has the form of the Inverse Faraday Effect. Finally, we present a numerical analysis which shows that DC magnetization has a maximum value and a saturation value for increasing values of the electric field amplitude E0. We find magnetization values between 1.68 × 10−13 A and 3.58 × 10−6 A within an experimental range of applied laser intensities and wavelengths. We also find a theoretical saturation value of 1.07 × 10−4 A for this magnetization. Our result shows that not only can DC magnetization be induced in graphene, but within certain criteria, can be experimentally detected. This can open more possibilities for the use of graphene in the field of optomagnetics.