Ratchet effect in spatially modulated bilayer graphene: Signature of hydrodynamic transport

Abstract

The authors study here the transition between drift-diffusion and hydrodynamic regimes of ac electron transport in bilayer graphene, focusing on one of the most general photovoltaic phenomenon: the ratchet effect. Compared to conventional dc transport measurements, this effect offers a number of additional possibilities to probe hydrodynamic flow of the electron fluid. A signature of the hydrodynamic regime --- a very sharp frequency dependence of the generated ratchet current --- is clearly demonstrated experimentally, in excellent agreement with the developed theory.