Coulomb Drag as a Probe of Coupled Plasmon Modes in Parallel Quantum Wells

TL;DR

This paper theoretically demonstrates that Coulomb drag between parallel quantum wells is significantly enhanced by coupled plasmon modes at certain temperatures, with specific experimental signatures such as temperature dependence and well separation effects.

Contribution

It introduces a theoretical analysis of plasmon effects on Coulomb drag in coupled quantum wells, highlighting the role of acoustic and optic plasmon modes.

Findings

Drag rate is substantially enhanced by coupled plasmon modes at T > 0.2 T_F.

Sharp upturn in drag rate occurs at T ≈ 0.2 T_F due to acoustic mode.

Drag rate shows a d^{-3} dependence on well separation and peaks at matched Fermi velocities.

Abstract

We show theoretically that the Coulomb drag rate between two parallel quasi-two-dimensional electron gases is substantially enhanced by the coupled acoustic and optic plasmon modes of the system at temperatures $T \gtrsim 0.2T_F$ (where $T_F$ is the Fermi temperature) for experimentally relevant parameters. The acoustic mode causes a sharp upturn in the scaled drag rate as a function of temperature at $T \approx 0.2 T_F$. Other experimental signatures of plasmon-dominated drag are a $d^{-3}$ dependence on the well separation $d$, and a peak in the drag rate as a function of relative carrier densities at matched Fermi velocities.