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Following the discovery of Bose-Einstein condensation (BEC) in ultra cold atoms [E. Gosta, Nobel Lectures in Physics (2001-2005), World Scientific (2008)], there has been a huge experimental and theoretical push to try and illuminate a superfluid state of Wannier-Mott excitons. Excitons in quantum wells, generated by a laser pulse, typically diffuse only a few micrometers from the spot they are created. However, Butov et al. and Snoke et al. reported luminescence from indirect and direct excitons hundreds of micrometers away from the laser excitation spot in double and single quantum well (QW) structures at low temperatures. This luminescence appears as a ring around the laser spot with the dark region between the spot and the ring. Developing the theory of a free superflow of Bose-liquids we show that the macroscopic luminesce rings and the dark state are signatures of the coherent superflow of condensed excitons at temperatures below their Berezinskii-Kosterlitz-Thouless (BKT) transition temperature. To further verify the dark excitonic superflow we propose several keystone experiments, including interference of superflows from two laser spots, vortex formation, scanning of moving dipole moments, and a giant increase of the luminescence distance by applying one-dimensional confinement potential. These experiments combined with our theory will open a new avenue for creating and controlling superflow of coherent excitons on nanoscale.
We have theoretically studied exciton states and photoluminescence spectra of strained wurtzite AlGaN/GaN quantum-well heterostructures. The electron and hole energy spectra are obtained by numerically solving the Schrodinger equation, both for a sin
Indirect excitons (IXs) are bound pairs of electrons and holes confined in spatially separated layers. We present wide single quantum well (WSQW) heterostructures with high IX mobility, spectrally narrow IX emission, voltage-controllable IX energy, a
Photoheating of the gas in low-mass dark matter (DM) haloes prevents baryons from cooling, leaving the haloes free of stars. Gas in these dark haloes remains exposed to the ultraviolet background (UVB), and so is expected to emit via fluorescent reco
We describe the observation of the circular and linear photogalvanic effects in HgTe/CdHgTe quantum wells. The interband absorption of mid-infrared radiation as well as the intrasubband absorption of terahertz (THz) radiation in the QWs structures is
Excitons in alloyed nanowire quantum dots have unique spectra as shown here using atomistic calculations. The bright exciton splitting is triggered solely by alloying and despite cylindrical quantum dot shape reaches over $15~mu$eV, contrary to previ