Casimir force and frictional drag between graphene sheets

Abstract

Some years ago it was predicted that quantum fluctuations of the electromagnetic field produce the Casimir forces between macroscopic bodies. It has recently been shown that two non-contacting bodies moving relative to each other experience a friction due to the same quantum fluctuations of the electromagnetic field. However, until recent time there was no experimental evidence for or against this effect, because the predicted friction forces are very small, and precise measurements of quantum forces are incredibly difficultwith present technology. The existence of quantum friction is still debated even among theoreticians. However, the situation drastically changed with the discovery of a new material—graphene. We recently proposed that quantum friction can be observed in experiments studying electrical transport phenomena in nonsuspended graphene on dielectric substrate and by measuring frictional drag between graphene sheets. We investigate the dependence of the thermal Casimir force and the Casimir friction force between two graphene sheets on the drift velocity of the electrons in one graphene sheet.We show that the drift motion produces a measurable change of the thermalCasimir force due to theDoppler effect. The thermalCasimir force aswell as the Casimir friction are strongly enhanced in the case of resonant photon tunneling when the energy of the emitted photon coincides with the energy of electron-hole pair excitations. In the case of resonant photon tunneling, even for temperatures above room temperature the Casimir friction is dominated by quantum friction due to quantum fluctuations.