Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 8: Frustrated Magnets – Strong Spin-Orbit Coupling
TT 8.6: Talk
Monday, September 5, 2022, 18:30–18:45, H10
Spin-orbit excitons in the jeff=1/2 compound K2IrCl6 — •Philipp Warzanowski1, Marco Magnaterra1, Karolin Hopfer1, Christoph Sahle2, Marco Morreti Sala3, Giulio Monaco4, Petra Becker5, Ladislav Bohatý5, and Markus Grüninger1 — 1Inst. of Physics II, University of Cologne — 2European Synchrotron Radiation Facility, Grenoble Cedex, France — 3Dip. di Fisica, Politecnico di Milano, Italy — 4Dip. di Fisica e Astronomia, Università di Padova, Italy — 5Sect. Crystallography, Inst. of Geology and Mineralogy, University of Cologne
Spin-orbit entangled Mott insulators offer new playgrounds to explore novel ground states. Iridates with a t2g5 electron configuration are popular platforms to realize jeff =1/2 systems due to the large cubic crystal field and strong spin-orbit coupling. Spectroscopies, RIXS in particular, show that thus far all iridates harbour non-cubic crystal field distortions, which turn the ground state away from an ideal jeff = 1/2 state. In this context, the (globally) cubic compound K2IrCl6 is a promising candidate to host ideal jeff = 1/2 moments. However, both RIXS and infrared spectroscopy show a splitting of the spin-orbit exciton. Within a single-site scenario, we extract a spin-orbit coupling λ = 435 meV and a non-cubic crystal field Δ = 60 meV, yielding a ground state of 99.8% jeff = 1/2 character. To explore the origin of non-cubic distortions, we discuss the possible effects of i) librations [1], ii) the coupling to phonons, and iii) defects [2].
[1] N. Khan et al., Phys Rev B 103, 125158 (2021)
[2] S.-S. Bao et al., Inorg. Chem. 57, 13252 (2018)