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Advances in Condensed Matter Physics
Volume 2011, Article ID 727958, 22 pages
Review Article

Experimental Progress towards Probing the Ground State of an Electron-Hole Bilayer by Low-Temperature Transport

1Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
2Department of Electronic and Electrical Engineering, University College, London WC1E7JE, UK

Received 27 May 2010; Accepted 27 October 2010

Academic Editor: Milica Milovanovic

Copyright © 2011 K. Das Gupta et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Recently, it has been possible to design independently contacted electron-hole bilayers (EHBLs) with carrier densities < 5 Γ— 1 0 1 0  cm2 in each layer and a separation of 10–20 nm in a GaAs/AlGaAs system. In these EHBLs, the interlayer interaction can be stronger than the intralayer interactions. Theoretical works have indicated the possibility of a very rich phase diagram in EHBLs consisting of excitonic superfluid phases, charge density waves, and Wigner crystals. Experiments have revealed that the Coulomb drag on the hole layer shows strong nonmonotonic deviations from a ∼ 𝑇 2 behaviour expected for Fermi-liquids at low temperatures. Simultaneously, an unexpected insulating behaviour in the single-layer resistances (at a highly “metallic” regime with π‘˜ 𝐹 𝑙 > 5 0 0 ) also appears in both layers despite electron mobilities of above ∼ 1 0 6 c m 2 V βˆ’ 1 s βˆ’ 1 and hole mobilities over ∼ 1 0 5 c m 2 V βˆ’ 1 s βˆ’ 1 . Experimental data also indicates that the point of equal densities ( 𝑛 = 𝑝 ) is not special.