Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 29: Poster Session: Spintronics; Spin-controled transport; Topological insulators; Interfaces / Surfaces; Magnetic semiconductors

HL 29.28: Poster

Montag, 11. März 2013, 16:00–20:00, Poster A

Optical third-harmonic spectroscopy of the magnetic semiconductors EuSe and EuTe — •Marco Lafrentz¹, David Brunne¹, Benjamin Kaminski¹, Victor V. Pavlov², Andre B. Henriques³, Roman V. Pisarev², Dmitri R. Yakovlev¹, and Manfred Bayer¹ — ¹Technische Universität Dortmund — ²A. F. Ioffe Physical-Technical Institute — ³Instituto de Física, Universidade de São Paulo

EuX (X=O, S, Se, and Te) are magnetic semiconductors possessing the centrosymmetric crystal structure m3m of rock-salt type in which the second-harmonic generation is forbidden in the electric dipole approximation but the third-harmonic generation (THG) is allowed. We studied the THG spectra of EuSe and EuTe near the band gap at 2.1−2.6 eV and at higher energies up to 4 eV. The observed signals are attributed to four-photon THG processes involving specific combinations of electronic transitions between the 4f⁷ ground state at the top of the valence band and the excited 4f⁶5d¹ states of the Eu²⁺-ions forming the lowest conduction bands. Strong modifications of the THG intensity were observed in applied magnetic fields up to 10 T revealing the magnetic phases to play the leading role. Temperature, magnetic field, and rotational anisotropy measurements allow us to unambiguously separate the crystallographic and magnetic-field-induced contributions. In addition, we developed a microscopic quantum-mechanical model that is in good agreement with the experimental results.^1,2

¹ M. Lafrentz, et al., Phys. Rev. B 82, 235206 (2010).

² M. Lafrentz, et al., Phys. Rev. B 85, 035206 (2012).