Plasmon enhancement of Coulomb drag in double quantum well systems

TL;DR

This paper derives a comprehensive formula for Coulomb drag in double quantum wells, revealing that plasmon modes significantly enhance drag at certain temperatures and densities, with intralayer scattering also playing a crucial role.

Contribution

It provides a new theoretical expression for drag rate applicable to arbitrary intralayer scattering, highlighting plasmon effects and their dependence on temperature and density ratios.

Findings

Drag rate peaks at around 0.5 T_F due to plasmon enhancement.

Doping layer distance affects the drag rate by a factor of two.

Dynamical screening significantly increases drag at moderate temperatures.

Abstract

We derive an expression for the drag rate (i.e., interlayer momentum transfer rate) for carriers in two coupled two-dimensional gases to lowest nonvanishing order in the screened interlayer electron--electron interaction, valid for {\sl arbitrary} intralayer scattering mechanisms, using the Boltzmann transport equation. We calculate the drag rate for experimentally relevant parameters, and show that for moderately high temperatures ($T\gtrsim 0.2 T_F$, where $T_F$ is the Fermi temperature) the dynamical screening of the interlayer results in a large enhancement of the drag rate due to the presence of coupled plasmon modes. This plasmon enhancement causes the scaled drag rate to have a peak (i) as a function of temperature at $T \approx 0.5 T_F$, and (ii) as a function of the ratio of densities of the carriers in the two layers when their Fermi velocities are equal. We also show that the drag rate can be significantly affected by the {\sl intralayer} scattering mechanisms; in particular, the drag rate changes approximately by a factor of 2 when the dopant layer modulation doped structures are moved in from 400~\AA to 100~\AA.