Josephson-like tunnel resonance and large Coulomb drag in GaAs-based electron-hole bilayers

Abstract

Bilayers consisting of two-dimensional (2D) electron and hole gases separated by a 10 nm thick AlGaAs barrier are formed by charge accumulation in epitaxially grown GaAs. Both vertical and lateral electric transport are measured in the millikelvin temperature range. The conductivity between the layers shows a sharp tunnel resonance at a density of $1.1\cdot 10^{10}{\text{ cm}}^{-2}$, which is consistent with a Josephson-like enhanced tunnel conductance. The tunnel resonance disappears with increasing densities and the two 2D charge gases start to show 2D-Fermi-gas behavior. Interlayer interactions persist causing a positive drag voltage that is very large at small densities. The transition from the Josephson-like tunnel resonance to the Fermi-gas behavior is interpreted as a phase transition from an exciton gas in the Bose-Einstein-condensate state to a degenerate electron-hole Fermi gas.

Updated after reviewer comments

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Cited by in corpus (7)

• Eliashberg theory for dynamical screening in bilayer exciton condensation
• Interaction and coherence in 2D bilayers
• Excitonic phases in a spatially separated electron-hole ladder model
• Correlated insulator in two Coulomb-coupled quantum wires
• Energetic comparison of exciton gas versus electron-hole plasma in a bilayer two-dimensional electron-hole system
• 2D bilayer electron-hole superfluidity with unequal and anisotropic masses
• Longitudinal Josephson effect in systems with pairing of spatially separated electrons and holes