Regensburg 2019 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 32: Spintronics
HL 32.5: Vortrag
Mittwoch, 3. April 2019, 16:00–16:15, H33
Thermal fluctuations cause spin-polarized states in the semiconducting lead halide perovskite (CH3NH3)PbI3 — •Daniel Niesner1, Martin Hauck2, Shreetu Shrestha3, Ievgen Levchuk3, Gebhard Matt3, Andres Osvet3, Miroslaw Batentschuk3, Christoph Brabec3, Heiko Weber2, and Thomas Fauster1 — 1Lehrstuhl für Festkörperphysik, Univ. of Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen — 2Lehrstuhl für Angewandte Physik, Univ. of Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen — 3i-Meet, Department of Materials Science, Univ. of Erlangen-Nürnberg, Martensstr. 7, D-91058 Erlangen
(CH3NH3)PbI3 is the prototypical lead halide perovskite used in thin-film photovoltaics. It is a direct semiconductor with single, non-degenerate valence and conduction bands. At 165 K, it undergoes a phase transition from a structure with antiferroelectric order into a phase with polar disorder and inversion symmetry on average. Performing photocurrent experiments with circularly polarized light, we find a circular photogalvanic effect in this phase, i. e. the current depends on the light helicity [1]. This implies the optical excitation of spin currents, an unexpected process for a centrosymmetric crystal. The effect gets stronger with increasing temperature, pointing towards a dynamical Rashba effect, i. e. a local symmetry breaking due to thermal fluctuations caused by large-amplitude, soft phonon modes. The dynamical Rashba effect is expected to be general to centrosymmetric materials with large-amplitude phonon modes containing heavy elements.
[1] D. Niesner et al., Proc. Natl. Acad. Sci. 115, 9505 (2018)