Observation of preformed electron-hole Cooper pairs in highly excited ZnO

Electrons and holes in a semiconductor form hydrogen-atom-like bound states, called excitons. At high electron-hole densities the attractive Coulomb force becomes screened and excitons can no longer exist. BCS theory predicts that at such high densities cooperative many-body effects can at low tempe...

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Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2012-05, Vol.85 (19), Article 195206
Main Authors: Versteegh, Marijn A. M., van Lange, A. J., Stoof, H. T. C., Dijkhuis, Jaap I.
Format: Article
Language:English
Subjects:
Condensed matter
Cooper pairs
Crossovers
Density
Excitons
Semiconductors
Stimulated emission
Zinc oxide
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Summary:Electrons and holes in a semiconductor form hydrogen-atom-like bound states, called excitons. At high electron-hole densities the attractive Coulomb force becomes screened and excitons can no longer exist. BCS theory predicts that at such high densities cooperative many-body effects can at low temperatures induce a bound state, an electron-hole Cooper pair, comparable to an electron-electron Cooper pair in a superconductor. Here we report the observation of preformed electron-hole Cooper pairs in a semiconductor. By measuring stimulated emission from a dense electron-hole gas in ZnO, we have explored both the crossover from the electron-hole plasma to the preformed Cooper-pair regime, and the crossover from the exciton to the preformed Cooper-pair regime.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.85.195206