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Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 49: Ultrafast Phenomena

HL 49.3: Talk

Wednesday, March 28, 2012, 10:00–10:15, EW 202

THz control of matter states: Coherent excitons beyond the Rabi-splitting — •Benjamin Ewers1, Niko S. Köster1, Ronja Woscholski1, Martin Koch1, Sangam Chatterjee1, Galina Khitrova2, Hyatt M. Gibbs2, Andrea C. Klettke3, Mackillo Kira3, and Stephan W. Koch31Faculty of Physics and Materials Sciences Center, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany — 2College of Optical Sciences, The University of Arizona, 1630 E. University Blvd., Tucson, Az, 85719-0094, USA — 3Faculty of Physics and Materials Sciences Center, Philipps-Universität Marburg, Mainzer Gasse 33, D-35032 Marburg, Germany

Strong external electromagnetic fields can be used to induce highly nonlinear modifications of the electronic matter states. We show experimentally and theoretically how optically induced excitonic polarization in semiconductors is modified and controlled by intense, single-cycle terahertz (THz) pulses. A resonant low-intensity excitation of GaAs-type direct-gap semiconductors induces coherent excitons with s-like orbital symmetry. The additional application of an electromagnetic field in the range of THz frequencies allows for a direct coupling of the coherent excitons to polarization states with p-type symmetry. By monitoring the low-intensity optical pulse we find a pronounced bleaching of the 1s-exciton resonance, a THz-induced Rabi-splitting, and a pronounced modulation on the high-energy side of the 1s-exciton resonance. All these features are fully explained by our quantum-mechanical many-body theory.

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