Abstract
Recent observations of possible signatures of Bose-Einstein condensation and superfluidity of excitons have drawn a lot of attention to excitonic bilayer systems. An exciton bilayer is a two-dimensional device where there are two conducting layers, one doped with electrons and one with holes, separated by few nanometers. In the last decade there has been a huge search effort to find superfluid phases in exciton bilayers, and there are experimental indications of a superfluid phase but to date the evidence is not clear. The aim of this project is to investigate three definitive fingerprints of exciton superfluidity: identification-markers. 1) We propose to employ the Josephson effect in exciton bilayers taken for the first time in combination with Coulomb drag measurements to definitively identify superfluidity. 2) Mapping out the collective modes in the various phases of the exciton bilayer system at different temperatures and densities. Characterization of the excitation spectra (i) in the exciton superfluid, (ii) exciton normal-fluid and (iii) decoupled normal-fluid phases. 3) Examination of the pseudogap region as a function of temperature and density. This is a vital high-temperature precursor of the superfluid transition. This understanding will provide a new theoretical basis for the experiments that aim to map out the various phases in the exciton bilayer system.
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