Anomalous Coulomb drag in electron-hole bilayers

TL;DR

This study investigates Coulomb drag in GaAs-AlGaAs electron-hole bilayers at very low temperatures, revealing anomalous behaviors that challenge existing Fermi-liquid theories and reciprocity principles.

Contribution

It provides new experimental insights into Coulomb drag phenomena in electron-hole bilayers, highlighting unexpected asymmetries and deviations from theoretical expectations.

Findings

Drag on hole layer shows an upturn below 1K

Effect is weaker or absent in electron layer

Results contradict Onsager's reciprocity theorem

Abstract

We report Coulomb drag measurements on GaAs-AlGaAs electron-hole bilayers. The two layers are separated by a 10 or 25nm barrier. Below T$\approx$1K we find two features that a Fermi-liquid picture cannot explain. First, the drag on the hole layer shows an upturn, which may be followed by a downturn. Second, the effect is either absent or much weaker in the electron layer, even though the measurements are within the linear response regime. Correlated phases have been anticipated in these, but surprisingly, the experimental results appear to contradict Onsager's reciprocity theorem.