Strongly Enhanced Hole-Phonon Coupling in the Metallic State of the Dilute Two-Dimensional Hole Gas

TL;DR

This study reveals a significant enhancement of hole-phonon coupling in dilute 2D GaAs hole systems, with a crossover from piezoelectric to deformation potential coupling and unexpectedly strong short-range interactions.

Contribution

It demonstrates that short-range deformation potential coupling is nearly twenty times stronger than theoretical predictions in the metallic state of dilute 2D hole gases.

Findings

Crossover from PZ to DP coupling above 100mK

DP coupling is much stronger than expected

Lower density holes cool more easily than higher density ones

Abstract

We have studied the temperature dependent phonon emission rate $P$($T$) of a strongly interacting ($r_s\geq$22) dilute 2D GaAs hole system using a standard carrier heating technique. In the still poorly understood metallic state, we observe that $P$($T$) changes from $P$($T$)$\sim T^5$ to $P$($T$)$\sim T^7$ above 100mK, indicating a crossover from screened piezoelectric(PZ) coupling to screened deformation potential(DP) coupling for hole-phonon scattering. Quantitative comparison with theory shows that the long range PZ coupling between holes and phonons has the expected magnitude; however, in the metallic state, the short range DP coupling between holes and phonons is {\it almost twenty times stronger} than expected from theory. The density dependence of $P$($T$) shows that it is {\it easier} to cool low density 2D holes in GaAs than higher density 2D hole systems.