Exciton transport in Cu2O: phonon wind versus superfluidity. & Exciton condensation with spontaneous time-reversal symmetry breaking Preprint at (2008) Excitonic charge-density-wave instability of spatially separated electron-hole layers in strong magnetic fields. Macroscopically ordered state in an exciton system. Stimulated scattering of indirect excitons in coupled quantum wells: signature of a degenerate Bose-gas of excitons. & Kopaev Possible instability of the semimetallic state toward Coulomb interaction. Collective properties of excitons in semiconductors. Bose-Einstein condensation and liquid helium. When atoms behave as waves: Bose-Einstein condensation and the atom laser. Bose-Einstein condensation in a dilute gas, the first 70 years and some recent experiments. All these phenomena emerge when the exciton gas is cooled below a few kelvin.Ĭornell, E. We also observed phase singularities in the coherent exciton gas. A pattern of extended spontaneous coherence is correlated with a pattern of spontaneous polarization, revealing the properties of a multicomponent coherent state. The coherence length in these regions is much larger than in a classical gas, indicating a coherent state with a much narrower than classical exciton distribution in momentum space, characteristic of a condensate. We found that spontaneous coherence of excitons emerges in the region of the macroscopically ordered exciton state 7 and in the region of vortices of linear polarization. Here we report measurements of spontaneous coherence in a gas of indirect excitons. Cold exciton gases can be realized in a system of indirect excitons, which can cool down below the temperature of quantum degeneracy owing to their long lifetimes 6. Excitons-bound pairs of electrons and holes-form a model system to explore the quantum physics of cold bosons in solids 4, 5. Spontaneous coherence is the key characteristic of condensation in momentum space 3. Spontaneous coherence of matter waves forms the basis of a number of fundamental phenomena in physics, including superconductivity, superfluidity and Bose–Einstein condensation 1, 2. If bosonic particles are cooled down below the temperature of quantum degeneracy, they can spontaneously form a coherent state in which individual matter waves synchronize and combine.
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