Structural fluctuations cause spin-split states in tetragonal (CH3NH3)PbI3 as evidenced by the circular photogalvanic effect

Journal article
(Original article)


Publication Details

Author(s): Niesner D, Hauck M, Shrestha S, Levchuk I, Matt G, Osvet A, Batentschuk M, Brabec C, Weber HB, Fauster T
Journal: Proceedings of the National Academy of Sciences
Publication year: 2018
Volume: 115
Journal issue: 38
Pages range: 9509-9514
ISSN: 0027-8424
eISSN: 1091-6490
Language: English


Abstract

Lead halide perovskites are used in thin-film solar cells, which owe their high efficiency to the long lifetimes of photocarriers. Various calculations find that a dynamical Rashba effect could significantly contribute to these long lifetimes. This effect is predicted to cause a spin splitting of the electronic bands of inversion-symmetric crystalline materials at finite temperatures, resulting in a slightly indirect band gap. Direct experimental evidence of the existence or the strength of the spin splitting is lacking. Here, we resonantly excite photocurrents in single crystalline (CH3NH3)PbI3 with circularly polarized light to clarify the existence of spin splittings in the band structure. We observe a circular photogalvanic effect, i.e., the photocurrent depends on the light helicity, in both orthorhombic and tetragonal (CH3NH3)PbI3. At room temperature, the effect peaks for excitation photon energies ΔE=110 meV below the direct optical band gap. Temperature-dependent measurements reveal a sign change of the effect at the orthorhombic{ extendash}tetragonal phase transition, indicating different microscopic origins in the two phases. Within the tetragonal phase, both ΔE and the amplitude of the circular photogalvanic effect increase with temperature. Our findings support a dynamical Rashba effect in this phase, i.e., a spin splitting caused by thermally induced structural fluctuations which break inversion symmetry.


FAU Authors / FAU Editors

Batentschuk, Miroslaw PD Dr.-Ing.
Institute Materials for Electronics and Energy Technology (i-MEET)
Brabec, Christoph Prof. Dr.
Institute Materials for Electronics and Energy Technology (i-MEET)
Fauster, Thomas Prof. Dr.
Lehrstuhl für Festkörperphysik
Hauck, Martin
Lehrstuhl für Angewandte Physik
Levchuk, Ievgen
Institute Materials for Electronics and Energy Technology (i-MEET)
Matt, Gebhard Dr.
Institute Materials for Electronics and Energy Technology (i-MEET)
Niesner, Daniel Dr.
Lehrstuhl für Festkörperphysik
Osvet, Andres Dr.
Institute Materials for Electronics and Energy Technology (i-MEET)
Shrestha, Shreetu
Institute Materials for Electronics and Energy Technology (i-MEET)
Weber, Heiko B. Prof. Dr.
Lehrstuhl für Angewandte Physik


Research Fields

Lead halide perovskites
Lehrstuhl für Festkörperphysik
Light-Matter Interaction in the Terahertz Range (Dr. Malzer, Prof. Weber)
Lehrstuhl für Angewandte Physik
Neue Materialien und Prozesse
Research focus area of a faculty: Technische Fakultät


How to cite

APA:
Niesner, D., Hauck, M., Shrestha, S., Levchuk, I., Matt, G., Osvet, A.,... Fauster, T. (2018). Structural fluctuations cause spin-split states in tetragonal (CH3NH3)PbI3 as evidenced by the circular photogalvanic effect. Proceedings of the National Academy of Sciences, 115(38), 9509-9514. https://dx.doi.org/10.1073/pnas.1805422115

MLA:
Niesner, Daniel, et al. "Structural fluctuations cause spin-split states in tetragonal (CH3NH3)PbI3 as evidenced by the circular photogalvanic effect." Proceedings of the National Academy of Sciences 115.38 (2018): 9509-9514.

BibTeX: 

Last updated on 2019-02-01 at 14:10