Abstract
We use interlayer tunneling to study bilayer two-dimensional electron systems at over a wide range of charge-density imbalance between the two layers. We find that the strongly enhanced tunneling associated with the coherent excitonic phase at small layer separation can survive at least up to an imbalance of , i.e., . Phase transitions between the excitonic state and bilayer states which lack significant interlayer correlations can be induced in three different ways: by increasing the effective interlayer spacing , the temperature , or the charge imbalance . We observe that close to the phase boundary the coherent phase can be absent at , present at intermediate , and then absent again at large , thus indicating an intricate phase competition between it and incoherent quasi-independent layer states. At zero imbalance, the critical shifts linearly with temperature, while at the critical is only weakly dependent on . At we report on an observation of a direct phase transition between the coherent excitonic bilayer integer quantum Hall phase and the pair of single-layer fractional quantized Hall states at and .
1 More- Received 8 August 2008
DOI:https://doi.org/10.1103/PhysRevB.78.205310
©2008 American Physical Society
Synopsis
A superfluid of excitons
Published 12 November 2008
Researchers explore how the excitonic condensate phase in a bilayer electron gas depends on the relative electron densities of the two layers.
See more in Physics