Ratchet effects in two-dimensional systems with a lateral periodic potential

TL;DR

This paper theoretically investigates radiation-induced ratchet currents in graphene with a lateral periodic potential, revealing how different scattering mechanisms and polarization states influence the current's magnitude and direction.

Contribution

It introduces a detailed theoretical model of ratchet currents in graphene considering various scattering mechanisms and polarization effects, expanding understanding of noncentrosymmetric systems.

Findings

Ratchet current has polarization-independent and polarization-sensitive components.

Short-range defects induce helicity-dependent ratchet currents.

Coulomb impurities suppress ratchet currents for certain polarization orientations.

Abstract

Radiation-induced ratchet electric currents have been studied theoretically in graphene with a periodic noncentrosymmetric lateral potential. The ratchet current generated under normal incidence is shown to consist of two contributions, one of them being polarization-independent and proportional to the energy relaxation time, and another controlled solely by elastic scattering processes and sensitive to both the linear and circular polarization of radiation. Two realistic mechanisms of electron scattering in graphene are considered. For short-range defects, the ratchet current is helicity-dependent but independent of the direction of linear polarization. For the Coulomb impurity scattering, the ratchet current is forbidden for the radiation linearly polarized in the plane perpendicular to the lateral-potential modulation direction. For comparison, the ratchet currents in a quantum well with a lateral superlattice are calculated at low temperatures with allowance for the dependence of the momentum relaxation time on the electron energy.