Carrier dynamics in Landau-quantized graphene featuring strong Auger scattering

The energy spectrum of common two-dimensional electron gases consists of a harmonic (that is, equidistant) ladder of Landau levels, thus preventing the possibility of optically addressing individual transitions. In graphene, however, owing to its non-harmonic spectrum, individual levels can be addre...

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Vydáno v:	Nature physics Ročník 11; číslo 1; s. 75 - 81
Hlavní autoři:	Mittendorff, Martin, Wendler, Florian, Malic, Ermin, Knorr, Andreas, Orlita, Milan, Potemski, Marek, Berger, Claire, de Heer, Walter A., Schneider, Harald, Helm, Manfred, Winnerl, Stephan
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	London Nature Publishing Group UK 01.01.2015 Nature Publishing Group Nature Publishing Group [2005-....]
Témata:	140/125 639/624/399/918 639/766/119/995 639/766/119/997 Atomic Augers Carriers Classical and Continuum Physics Complex Systems Condensed Matter Condensed Matter Physics Depletion Dynamics Graphene Ladders Magnetic fields Materials science Mathematical and Computational Physics Mesoscopic Systems and Quantum Hall Effect Molecular Optical and Plasma Physics Optical pumping Physics Quantum physics Scattering Theoretical Two dimensional
ISSN:	1745-2473, 1745-2481
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Popis
Shrnutí:	The energy spectrum of common two-dimensional electron gases consists of a harmonic (that is, equidistant) ladder of Landau levels, thus preventing the possibility of optically addressing individual transitions. In graphene, however, owing to its non-harmonic spectrum, individual levels can be addressed selectively. Here, we report a time-resolved experiment directly pumping discrete Landau levels in graphene. Energetically degenerate Landau-level transitions from n = −1 to n = 0 and from n = 0 to n = 1 are distinguished by applying circularly polarized THz light. An analysis based on a microscopic theory shows that the zeroth Landau level is actually depleted by strong Auger scattering, even though it is optically pumped at the same time. The surprisingly strong electron–electron interaction responsible for this effect is directly evidenced through a sign reversal of the pump–probe signal. Landau levels in graphene are not equidistant so that transitions between them can be individually probed. Time-resolved optical pumping experiments reveal strong electron–electron scattering resulting in an Auger-depleted zeroth order Landau level.
Bibliografie:	SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 14 ObjectType-Article-1 ObjectType-Feature-2 content type line 23
ISSN:	1745-2473 1745-2481
DOI:	10.1038/nphys3164