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

Abstract

We report single layer resistivities of two-dimensional electron and hole gases in an electron-hole bilayer with a 10 nm barrier. In a regime where the interlayer interaction is stronger than the intralayer interaction, we find that an insulating state $(d\ensuremath{\rho}/dT<0)$ emerges at $T\ensuremath{\sim}1.5\text{ }\text{K}$ 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 localization 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 Liu et al. [Phys. Rev. B 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 [Ludwig et al., Contrib. Plasma Phys. 47, 335 (2007)]