Dresden 2017 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 42: Correlated Electrons: Frustrated Magnets - Strong Spin-Orbit Coupling 2

TT 42.9: Talk

Wednesday, March 22, 2017, 11:45–12:00, HSZ 304

Single, double, and triple spin-orbit excitons in α-RuCl₃ — •Nick Borgwardt¹, Alessandro Revelli¹, Maria Hermann², Petra Becker³, Paul van Loosdrecht¹, and Markus Grüninger¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²Institut für theoretische Physik, Universität zu Köln — ³Abteilung Kristallographie, Institut für Geologie und Mineralogie, Universität zu Köln

Spin-orbit-assisted d⁵ Mott insulators with local j=1/2 moments are discussed as realizations of the Kitaev model which hosts Majorana fermion excitations. In promising candidate materials such as RuCl₃, lattice distortions give rise to a mixing of j=1/2 and 3/2 character which may spoil the picture. The so-called spin-orbit exciton corresponds to an excitation to the j=3/2 state and is very sensitive to the character of the relevant states. In the literature, features in Raman scattering, neutron scattering, and infrared absorption data were reported in the relevant frequency range of one to a few hundred meV. We challenge the reported interpretations and demonstrate that our infrared data show single, double, and triple spin-orbit excitons. These novel and unusual excitations are directly connected to the microscopic processes relevant for the Kitaev coupling.