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HL: Fachverband Halbleiterphysik

HL 42: Oxide semiconductors

HL 42.3: Vortrag

Mittwoch, 18. März 2020, 10:00–10:15, POT 51

Magnetic-field-induced second harmonic generation of excitons in Cu₂O — •Andreas Farenbruch, Johannes Mund, Dietmar Fröhlich, Dmitri Yakovlev, and Manfred Bayer — Experimentelle Physik 2, Technische Universität Dortmund, Germany

We report on magnetic-field-induced second harmonic generation (SHG) of higher excitons (n ≥ 3) of the lowest exciton series in Cu₂O. SHG is allowed for the 1S orthoexciton and higher excitons in low symmetry directions (e.g. [111] and [112]). By application of a magnetic field in Voigt geometry SHG gets also allowed for excitation along the [110]-axis. Magnetic-field experiments in Voigt configuration are of special interest, since one expects besides the Zeeman effect also the magneto-Stark effect, which leads to an effective electric field perpendicular to the light propagation and magnetic-field direction. With a group theoretical analysis we derive polarization selection rules for SHG. Of special elegance are 2D polarization diagrams (SHG intensity versus incoming and outgoing polarization angle). By a special choice of the experimental settings one can separate the spectral features due to the Zeeman effect and the magneto-Stark effect or observe an interference of both effects. The SHG signals are large enough to measure the full polarization dependence for the whole spectrum. It is shown, that the magneto-Stark effect dominates the Zeeman effect for higher principal quantum numbers.