Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 35: Ultrafast Phenomena I
O 35.11: Talk
Tuesday, March 8, 2016, 12:45–13:00, H10
Nonlinear terahertz quantum control of Landau-quantized electrons — •Thomas Maag1, Andreas Bayer1, Sebastian Baierl1, Matthias Hohenleutner1, Tobias Korn1, Christian Schüller1, Dominique Bougeard1, Christoph Lange1, Rupert Huber1, Martin Mootz2, Stephan W. Koch2, and Mackillo Kira2 — 1Department of Physics, University of Regensburg, 93053 Regensburg, Germany — 2Department of Physics, Philipps-University Marburg, 35032 Marburg, Germany
Controlling superpositions of many-body electronic quantum states in solids is impeded by rapid dephasing through inter-particle scattering. However, Walter Kohn found in 1961 that the cyclotron resonance of Landau-quantized electrons in a two-dimensional electron gas (2DEG) is immune to Coulomb forces. This protection warrants long coherence times and makes the system interesting for quantum control, but explicitly excludes nonlinearities. Here, we demonstrate how intense light pulses in the terahertz (THz) spectral range can induce well-controlled electronic many-body correlations in a magnetically biased 2DEG and tailor a distinctly anharmonic response. Coherent ladder climbing up to the 6th rung yields population inversion and abruptly increases dephasing. Strikingly, 2D THz spectroscopy reveals distinct multi-wave mixing signatures, which our quantum theory explains through Coulomb interactions between electrons and the positively charged ionic background. These many-body dynamics demonstrate how internal degrees of freedom of solid state quantum systems enable coherent nonlinear interactions for future ultrafast quantum information processing.