Effect of radiation on transport in graphene

TL;DR

This paper investigates how electromagnetic radiation influences transport in graphene p-n junctions, revealing that radiation can suppress or generate current via dynamical gaps and photon-assisted tunneling, with implications for optoelectronic applications.

Contribution

It introduces a theoretical analysis of radiation-induced dynamical gaps in graphene junctions and predicts conditions for photocurrent generation without bias.

Findings

Radiation creates dynamical gaps proportional to EF amplitude.

Transmission can be fully suppressed by strong radiation.

Photocurrent can flow without bias when potential exceeds half photon energy.

Abstract

We study transport properties of graphene-based p-n junctions irradiated by an electromagnetic field (EF). The resonant interaction of propagating quasiparticles with an external monochromatic radiation opens dynamical gaps in their spectrum, resulting in a strong modification of current-voltage characteristics of the junctions. The values of the gaps are proportional to the amplitude of EF. We find that the transmission of the quasiparticles in the junctions is determined by the tunneling through the gaps, and can be fully suppressed when applying a sufficiently large radiation power. However, EF can not only suppress the current but also generate it. We demonstrate that if the height of the potential barrier exceeds a half of the photon energy, the directed current (photocurrent) flows through the junction without any dc bias voltage applied. Such a photocurrent arises as a result of inelastic quasiparticle tunneling assisted by one- or two-photon absorption. We calculate current-voltage characteristics of diverse graphene based junctions and estimate their parameters necessary for the experimental observation of the photocurrent and transmission suppression.