Optical phonon induced frictional drag in coupled two-dimensional electron gases

TL;DR

This paper investigates how optical phonons influence frictional drag between two isolated two-dimensional electron gases, highlighting their potential significance at high temperatures due to strong electron-phonon coupling.

Contribution

It provides a theoretical analysis of optical phonon effects on interlayer frictional drag, emphasizing differences from acoustic phonons and suggesting conditions for observable effects.

Findings

Optical phonons can significantly affect drag at high temperatures.

Short-range interaction due to negligible group velocity of optical phonons.

Potential observability in InSb or double subband GaAs systems.

Abstract

The role of optical-phonons in frictional drag between two adjacent but electrically isolated two-dimensional electron gases is investigated. Since the optical-phonons in III-V materials have a considerably larger coupling to electrons than acoustic phonons (which are the dominant drag mechanism at low T and large separations) it might be expected that the optical phonons will give a large effect high temperatures. The two key differences between optical and acoustic phonon mediated drag are: (1) the optical phonon mediated interlayer interaction is short-ranged due to their negligible group velocity at the Brillouin zone center; and (2) the typical momentum transfer for an optical phonon mediated scattering is relatively large. These considerations make optical phonon mediated drag difficult to see in single subband GaAs systems, but it may be possible to see the effect in double subband GaAs systems or single subband quantum wells in a material with a lower effective mass and lower optical phonon energy such as InSb.