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arXiv · 1610.01673

Electronic excitations stabilised by a degenerate electron gas in semiconductors

C. Nenstiel·G. Callsen·F. Nippert·T. Kure·M. R. Wagner·S. Schlichting·N. Jankowski·M. P. Hoffmann·S. Fritze·A. Dadgar·A. Krost·A. Hoffmann·F. Bechstedt
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Abstract

Excitons in semiconductors and insulators consist of fermionic subsystems, electrons and holes, whose attractive interaction facilitates bound quasiparticles with quasi-bosonic character due to even-numbered pair spins. In the presence of a degenerate electron gas, such excitons dissociate due to free carrier screening, leaving a spectrally broad and faint optical signature behind. Contrary to this expected behaviour, we have discovered pronounced emission traces in bulk, germanium-doped GaN up to 100 K, mimicking excitonic behaviour at high free electron concentrations from 3.4E19/cm3 to 8.9E19/cm3. Consequently, we show that a degenerate, three-dimensional electron gas stabilizes a novel class of quasiparticles, named collexons, by many-particle effects dominated by exchange of electrons with the Fermi gas. The observation of collexons and their stabilisation with rising doping concentration, is facilitated by a superior crystal quality due to perfect substitution of the host atom with the dopant.

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C. Nenstiel, G. Callsen, F. Nippert, T. Kure, M. R. Wagner, S. Schlichting, N. Jankowski, M. P. Hoffmann, S. Fritze, A. Dadgar, A. Krost, A. Hoffmann, F. Bechstedt. 2016-10-05. Electronic excitations stabilised by a degenerate electron gas in semiconductors. https://doi.org/10.1038/s42005-018-0033-4

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