Dresden 2020 – wissenschaftliches Programm
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TT 35.9: Vortrag
Mittwoch, 18. März 2020, 12:00–12:15, HSZ 304
On the charge transfer energy in iridates: a HAXPES study — •Daisuke Takegami1, Deepa Kasinathan1, Klaus Wolff1, Simone Altendorf1, Chun-Fu Chang1, Katharina Hoefer1, Anna Meléndez-Sans1, Yuki Utsumi1, Federico Meneghin1, Thai Duy Ha1, Chien-Han Yen1, Kai Chen2, Chang-Yang Kuo1,3, Yen-Fa Liao3, Ku-Ding Tsuei3, Ryan Morrow4, Sabine Wurmehl4, Beluvalli E. Prasad1, Martin Jansen5, Alexander Komarek1, Philipp Hansmann1, and Liu Hao Tjeng1 — 1MPI for Chemical Physics of Solids, Dresden, Germany — 2Institute of Physics II, University of Cologne, Cologne, Germany — 3National Synchrotron Radiation Research Center, Hsinchu, Taiwan — 4Leibniz Institute for Solid State and Materials Research IFW Dresden, Dresden, Germany — 5MPI for Solid State Research, Stuttgart, Germany
We have investigated the electronic structure of iridates in the double perovskite crystal structure containing either Ir4+ or Ir5+ using HAXPES. The experimental valence band spectra can be well reproduced using tight binding calculations including only the Ir 5d, O 2p and O 2s orbitals with parameters based on the down-folding of the DFT band structure results. We found that regardless the A and B cations, the A2BIrO6 iridates have essentially zero O 2p to Ir 5d charge transfer energies. They are extremely covalent systems with the consequence is that the magnetic exchange interactions become very long-ranged, thereby hampering the materialization of the Kitaev model. Nevertheless, it still would be possible to realize a spin-liquid system using the iridates with a proper tuning of the competing exchange interactions.