▎ 摘　　要

We study the frictional drag between two graphene layers placed inside a cavity. We show that the drag has two contributions: the well-known Coulomb drag, and a novel photon-mediated drag. The latter arises from a cavity-mediated interaction in which the backscattering is not suppressed and the screening is relatively weak. As a result, the photon-mediated drag resistivity in the Fermi-liquid regime acquires corrections to the usual quadratic temperature dependence, has a slow decay as the interlayer separation d increases, and depends on the carrier density n as rho D similar to 1/n(2). Thus, whereas for small d and n the Coulomb drag dominates, as these parameters increase the drag transitions to a purely photon-mediated drag. The onset of this transition depends on the electromagnetic field enhancement inside the cavity.