Coulomb drag in normal metals and superconductors: Diagrammatic approach

Abstract

The diagrammatic linear response formalism for the Coulomb drag in two{layer systems is developed. This technique can be used to treat both elastic disorder and intralayer interaction e ects. In the absence of intralayer electron{electron correlations we reproduce earlier results, obtained using the kinetic equation and the memory{function formalism. In addition we calculate weak{localization corrections to the drag coe cient and the Hall drag coe cient in a perpendicular magnetic eld. As an example of the intralayer interaction e ects we consider a situation where one (or both) layers are close to (but above) the superconducting transition temperature. Fluctuation corrections, analogous to the Aslamazov{Larkin corrections, to the drag coecient are calculated. Although the uctuation corrections do not enhance the drag coe cient for normal{superconductor systems, a dramatic enhancement is found for superconductor{superconductor structures.Typeset using REVT E X 1

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

“…47 to include effects due to the finite width of the GaAs quantum well (see Supplementary Note 4). This shows that the experimental results in this temperature range are consistent with the canonical Fermi-liquid prediction 24,[43][44][45][46][47][48][49][50] , that is, R D pT 2 (see also Fig. 3a), as constrained by the available phase-space of the initial and final states involved in the scattering process.…”

“…We therefore exclude that this effect is responsible for the logarithmic increase. Finally, the disorder effects in the diffusive regime 49,50 do lead to a logarithmic enhancement of the drag signal of the form R D (T)p À T 2 log(T) for T-0, which is therefore a correction to the Fermi-liquid behaviour and not an upturn.…”

Many-body effects in the Coulomb drag between low density electron layers

“…The STLS approximation on the other hand overestimates it. A theoretical model based on the formulation of Vignale and Singwi [15] describing the intra-layer correlations via a local-field factor within the Hubbard approximation yields very good quantitative agreement with the experimental data. Also important is to include the inter-layer correlations through the local-field factor G 12 : In particular, the temperature dependence of r D at fixed layer densities and density dependence at fixed temperatures within the VS approach is accurately reproduced.…”

“…These include the Boltzmann equation [14], the memory function formalism [6], and diagrammatic perturbation theory [15]. Theoretical considerations lead to the same expression for r D in terms of the effective interlayer interaction.…”

“…Theoretical considerations lead to the same expression for r D in terms of the effective interlayer interaction. To the lowest order in the dynamically screened effective inter-layer interaction W 12 ðq; vÞ; and specializing to the case of equal densities in the layers, r D is given as [6,9,14,15] …”