Laser-assisted spin-polarized transport in graphene tunnel junctions

TL;DR

This paper theoretically investigates how laser irradiation influences spin-polarized electron transport in graphene tunnel junctions, revealing photon-assisted tunneling, tunable dynamical gaps, and oscillatory tunnel magnetoresistance effects.

Contribution

It introduces a comprehensive theoretical analysis of laser effects on spin transport in graphene, highlighting photon-assisted processes and tunable dynamical gaps.

Findings

Resonant peaks in differential conductance due to photon-assisted tunneling.

Dynamical gap around zero bias tunable by laser parameters.

Oscillatory behavior of tunnel magnetoresistance influenced by external fields.

Abstract

Keldysh nonequilibrium Green's function method is utilized to study theoretically the spin polarized transport through a graphene spin valve irradiated by a monochromatic laser field. It is found that the bias dependence of the differential conductance exhibits successive peaks corresponding to the resonant tunneling through the photon-assisted sidebands. The multi photon processes originate from the combined effects of the radiation field and the graphene tunneling properties, and are shown to be substantially suppressed in a graphene spin valve which results in a decrease of the differential conductance for a high bias voltage. We also discussed the appearance of a dynamical gap around zero bias due to the radiation field. The gap width can be tuned by changing the radiation electric field strength and the frequency. This leads to a shift of the resonant peaks in the differential conductance. We also demonstrate numerically the dependencies of the radiation and spin valve effects on the parameters of the external fields and those of the electrodes. We find that the combined effects of the radiation field, the graphene, and the spin valve properties bring about an oscillatory behavior in the tunnel magnetoresistance (TMR), and this oscillatory amplitude can be changed by scanning the radiation field strength and/or the frequency.