Search

We present a unified Boltzmann transport theory for the drag resistivity ρD in two-component systems close to a second-order phase transition. We find general expressions for ρD in two and three spatial dimensions, for arbitrary population and mass imbalance, for particle- and holelike bands, and show how to incorporate, at the Gaussian level, the effect of fluctuations close to a phase transition. We find that the proximity to the phase transition enhances the drag resistivity upon approaching the critical temperature from above, and we qualitatively derive the temperature dependence of this enhancement for various cases. In addition, we present numerical results for two concrete experimental systems: (i) three-dimensional cold atomic Fermi gases close to a Stoner transition and (ii) two-dimensional spatially separated electron and hole systems in semiconductor double quantum wells [ABSTRACT FROM AUTHOR]

The onset of exciton condensation in a topological insulator thin film was recently predicted. We calculate the critical temperature for this transition, taking into account screening effects. Furthermore, we show that the proximity to this transition can be probed by measuring the Coulomb drag resistivity between the surfaces of the thin film as a function of temperature. This resistivity shows an upturn upon approaching the exciton-condensed state. [ABSTRACT FROM AUTHOR]

We examine the influence of remote bands on the tendency toward exciton condensation in a system consisting of two parallel graphene layers with negligible interlayer tunneling. We find that the remote bands can play a crucial supporting role, especially at low carrier densities, and comment on some challenges that arise in attempting quantitative estimates of condensation temperatures. [ABSTRACT FROM AUTHOR]