Cyclotron- and magnetoplasmon resonances in bilayer graphene ratchets

TL;DR

This paper demonstrates tunable terahertz-to-dc conversion in bilayer graphene via ratchet effects, revealing cyclotron resonance and plasmonic phenomena influenced by electron interactions, supported by experimental data and theoretical modeling.

Contribution

It provides the first experimental observation of cyclotron resonance in graphene ratchets and introduces a hydrodynamic model explaining the observed effects.

Findings

Observation of sharp cyclotron resonance in photocurrent

Detection of plasmonic splitting due to Coulomb interactions

Partial suppression of second harmonic by electron collisions

Abstract

We report on a tunable - by magnetic field and gate voltage - conversion of terahertz radiation into a dc current in spatially modulated bilayer graphene. We experimentally demonstrate that the underlying physics is related to the so-called ratchet effect. Our key findings are the direct observation of a sharp cyclotron resonance in the photocurrent and the demonstration of two effects caused by electron-electron interaction: the plasmonic splitting of the resonance due to long-range Coulomb coupling and the partial suppression of its second harmonic due to fast interparticle collisions. We develop a theory which perfectly fits our data. We argue that the ratchet current is generated in the hydrodynamic regime of non-ideal electron liquid.