Dresden 2020 – wissenschaftliches Programm
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TT 17.11: Poster
Montag, 16. März 2020, 15:00–19:00, P2/EG
Multiple Spin-Orbit Excitons and the Electronic Structure of α-RuCl3 — •Philipp Warzanowski1, Nick Borgwardt1, Karolin Hopfer1, Thomas Koethe1, Petra Becker2, Vladimir Tsurkan3,4, Alois Loidl3, Maria Hermanns5, Paul H. M. van Loosdrecht1, and Markus Grüninger1 — 1Inst. of Physics II, University of Cologne — 2Sect. Crystallography, Inst. of Geology and Mineralogy, University of Cologne — 3Exp. Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg — 4Inst. of Applied Physics, Chisinau, Moldova — 5Dept. of Physics, Stockholm University, AlbaNova University Center, Sweden
α-RuCl3 is widely discussed as a proximate Kitaev spin-liquid material. This scenario builds upon spin-orbit entangled j=1/2 moments which arise in a t2g5 electron configuration with strong spin-orbit coupling λ and a large cubic crystal field. Despite the keen interest in α-RuCl3, the low-energy electronic structure is still puzzling. In particular the origin of infrared absorption features at 0.30, 0.53, and 0.75 eV is still a matter of debate. Also the energy of the spin-orbit exciton, the excitation from j=1/2 to j=3/2, and thus λ are controversial. Combining infrared absorption and Raman data, we attribute the infrared features to single, double, and triple spin-orbit excitons, yielding λ=0.16 eV and a non-cubic crystal field splitting Δ=42 meV. These results support the j=1/2 picture despite of the crystal field distortion. The strength of the double excitation can be understood by the same hopping interactions that also establish dominant Kitaev exchange .
 P. Warzanowski et al., arXiv:1911.09337