Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 50: Poster Session: Correlated Electrons 2

TT 50.8: Poster

Mittwoch, 3. April 2019, 15:00–18:30, Poster D

j=1/2 moments on the fcc lattice in Ba₂CeIrO₆ — Alessandro Revelli¹, •Chin Chyi Loo¹, Marco Moretti Sala², Giulio Monaco³, Tobias Fröhlich¹, Thomas Lorenz¹, Petra Becker⁴, Ladislav Bohatý⁴, Dominik Kiese⁵, Finn Lasse Büßen⁵, Jan Attig⁵, Sergey Streltsov⁶, Arun Paramekanti⁷, Markus Braden¹, Simon Trebst⁵, Paul van Loosdrecht¹, and Markus Grüninger¹ — ¹II. Physics Institute, University of Cologne — ²ESRF, Grenoble, France — ³Universita di Trento, Italy — ⁴Sect. Crystallography, Institute of Geology and Mineralogy, University of Cologne — ⁵Institute for Theoretical Physics, University of Cologne — ⁶Russian Academy of Sciences, Ekaterinburg, Russia — ⁷Department of Physics, University of Toronto, Canada

Spin-orbit-entangled j=1/2 iridates were predicted to host exotic quantum states, e.g. a Kitaev spin liquid. In real materials, deviations from cubic symmetry mix j=1/2 and 3/2 states, which may strongly affect the properties. We establish the double perovskite Ba₂CeIrO₆ as a nearly ideal model system for j=1/2 on an fcc lattice combining geometrical and exchange frustration. XRD finds an average cubic structure, while RIXS reveals the smallest crystal-field splitting observed thus far in 5d⁵ iridates, showing that the ground state has 98.4% j=1/2 character. Significant exchange interactions are supported by the large Curie-Weiss temperature, the dispersion of the j=3/2 states, and DFT results. We estimate the ratio of Kitaev to Heisenberg coupling as K/J=0.1-0.2. Magnetic order sets in at 14 K, while a theoretical study of the J₁-J₂-K model suggests that Ba₂CeIrO₆ is close to a spin liquid.