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HL: Fachverband Halbleiterphysik

HL 89: Optical Properties II

HL 89.2: Vortrag

Freitag, 18. März 2011, 10:30–10:45, POT 251

Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe — •David Brunne¹, Marco Lafrentz¹, Benjamin Kaminski¹, Victor Pavlov², Andre Henriques³, Roman Pisarev², Dmitri Yakovlev¹, and Manfred Bayer¹ — ¹TU Dortmund — ²A. F. Ioffe physical-technical Institute — ³Instituto de Fisica, Universidade de Sao Paulo

EuTe possesses the centrosymmetric crystal structure m3m of rock-salt type in which the second harmonic generation (SHG) is forbidden in electric-dipole approximation, but the third harmonic generation (THG) is allowed. We studied the THG spectra of this material and observed several resonances in the vicinity of the band gap at 2.2 − 2.5 eV and at higher energies up to 4 eV, which are related to four photon THG processes. The observed resonances are assigned to specfic combinations of electronic transitions between the ground 4f⁷ state at the top of valence band and excited 4f⁶5d¹ states of Eu²⁺ ions, which form the lowest energy conduction band. Temperature, magnetic field and rotational anisotropy studies allowed us to distinguish crystallographic and magnetic field induced contributions to the THG. A strong modification of the THG intensity was observed in applied magnetic fields at particular resonances due to interference of crystallographic and magnetic field induced contributions. A microscopic quantum mechanical model of the THG response was developed and its conclusions are in good agreement with the experimental results.