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TT: Fachverband Tiefe Temperaturen

TT 17: Poster Session Correlated Electrons 1

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 Tsurkan^3,4, 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 t_2g⁵ 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 [1].
[1] P. Warzanowski et al., arXiv:1911.09337