Can Hall drag be observed in Coulomb coupled quantum wells in a magnetic field

We study the transresistivity ρ21 (or equivalently, the drag rate) of two Coulomb-coupled quantum wells in the presence of a perpendicular magnetic field, using semi-classical transport theory. Elementary arguments seem to preclude any possibility of observation of "Hall drag" (i.e., a nonzero off-diagonal component in ρ21). We show that these arguments are specious, and in fact Hall drag can be observed at sufficiently high temperatures when the intralayer transport time τ has significant energy-dependence around the Fermi energy eF. The ratio of the Hall to longitudinal transresistivities goes as T2Bs, where T is the temperature, B is the magnetic field, and s = [δτ/δe](eF).