Terahertz and gigahertz magneto-ratchets in graphene-based 2D metamaterials

TL;DR

This study demonstrates giant, sign-alternating magneto-oscillations and resonant ratchet currents in graphene-based 2D metamaterials under terahertz/gigahertz excitation, linked to quantum effects and controlled by gate voltages.

Contribution

It provides the first experimental observation of magneto-ratchet effects in graphene metamaterials, with a developed theory explaining the interplay of near-field radiation and electrostatic potential.

Findings

Giant magneto-oscillations exceeding zero-field ratchet current

Resonant ratchet currents from cyclotron and spin resonances

Theoretical model matches experimental data

Abstract

We report on the observation and study of the magneto-ratchet effect in a graphene-based two-dimensional metamaterial formed by a graphite gate that is placed below a graphene monolayer and patterned with an array of triangular antidots. We demonstrate that terahertz/gigahertz excitation of the metamaterial leads to sign-alternating magneto-oscillations with an amplitude that exceeds the ratchet current at zero magnetic field by orders of magnitude. The oscillations are shown to be related to the Shubnikov-de Haas effect. In addition to the giant ratchet current oscillations we detect resonant ratchet currents caused by the cyclotron and electron spin resonances. The results are well described by the developed theory considering the magneto-ratchet effect caused by the interplay of the near-field radiation and the nonuniform periodic electrostatic potential of the metamaterial controlled by the gate voltages.