Possible effect of collective modes in zero magnetic field transport in an electron-hole bilayer

TL;DR

This study investigates the transport properties of electron-hole bilayers at low temperatures, revealing an insulating state likely due to a charge density wave phase driven by strong interlayer interactions.

Contribution

It provides experimental evidence of an insulating phase in electron-hole bilayers at low temperatures, supporting theoretical predictions of charge density wave formation.

Findings

Insulating state emerges below 1.5 K in strongly interacting bilayers.

Insulating behavior occurs deep in the metallic regime, challenging disorder-based localization explanations.

Results align with theoretical models predicting charge density waves in such systems.

Abstract

We report single layer resistivities of 2-dimensional electron and hole gases in an electron-hole bilayer with a 10nm barrier. In a regime where the interlayer interaction is stronger than the intralayer interaction, we find that an insulating state ($d\rho/dT < 0$) emerges at $T\sim1.5{\rm K}$ or lower, when both the layers are simultaneously present. This happens deep in the $"$metallic" regime, even in layers with $k_{F}l>500$, thus making conventional mechanisms of localisation due to disorder improbable. We suggest that this insulating state may be due to a charge density wave phase, as has been expected in electron-hole bilayers from the Singwi-Tosi-Land-Sj\"olander approximation based calculations of L. Liu {\it et al} [{\em Phys. Rev. B}, {\bf 53}, 7923 (1996)]. Our results are also in qualitative agreement with recent Path-Integral-Monte-Carlo simulations of a two component plasma in the low temperature regime [ P. Ludwig {\it et al}. {\em Contrib. Plasma Physics} {\bf 47}, No. 4-5, 335 (2007)]