Cyclotron and magnetoplasmon resonances in bilayer graphene ratchets

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 nonideal electron liquid.

Automated summary

We present a study on the conversion of terahertz radiation into a dc current in spatially modulated bilayer graphene, tunable by magnetic field and gate voltage. We observe a sharp cyclotron resonance in the photocurrent and discover two effects caused by electron-electron interaction: the splitting of the resonance due to Coulomb coupling and the suppression of its second harmonic due to interparticle collisions. A theoretical model that fits the experimental data perfectly is developed, suggesting that the ratchet current is generated in the hydrodynamic regime of nonideal electron liquid.