Terahertz electric field driven electric currents and ratchet effects in graphene

TL;DR

This paper investigates terahertz radiation-induced photocurrents in graphene, exploring various effects such as photon drag, photogalvanic, and ratchet effects, and demonstrates graphene's potential as a broadband terahertz detector.

Contribution

It provides a comprehensive experimental and theoretical analysis of terahertz-induced photocurrents and ratchet effects in graphene, including new insights into symmetry-dependent phenomena and device applications.

Findings

Photocurrents depend on polarization and incidence angle.

Enhanced photogalvanic effects in SiC's reststrahlen band.

Graphene can serve as a fast, broadband terahertz detector.

Abstract

Terahertz field induced photocurrents in graphene were studied experimentally and by microscopic modeling. Currents were generated by cw and pulsed laser radiation in large area as well as small-size exfoliated graphene samples. We review general symmetry considerations leading to photocurrents depending on linear and circular polarized radiation and then present a number of situations where photocurrents were detected. Starting with the photon drag effect under oblique incidence, we proceed to the photogalvanic effect enhancement in the reststrahlen band of SiC and edge-generated currents in graphene. Ratchet effects were considered for in-plane magnetic fields and a structure inversion asymmetry as well as ratchets by non-symmetric patterned top gates. Lastly, we demonstrate that graphene can be used as a fast, broadband detector of terahertz radiation.