Dresden 2020 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 4: Complex Oxides: Bulk Properties (jointly with DS, HL, KFM, MA, O) (joint session TT/HL/MA)

HL 4.2: Vortrag

Montag, 16. März 2020, 09:45–10:00, HSZ 201

Melting of excitonic dispersion in LaCoO₃: theory and experiment — Atsushi Hariki¹, Ru-Pan Wang², Andrii Sotnikov^1,3, Keisuke Tomiyasu⁴, Davide Betto⁵, Nicholas B. Brookes⁵, Yohei Uemura², Mahnaz Ghiasi², Frank M. F. de Groot², and •Jan Kuneš^1,6 — ¹Institute of Solid State Physics, TU Wien — ²Debye Institute for Nanomaterials Science, Utrecht University — ³Akhiezer Institute for Theoretical Physic, Kharkiv — ⁴Department of Physics, Tohoku University — ⁵European Synchrotron Radiation Facility, Grenoble — ⁶Institute of Physics, Czech Academy of Sciences

We present Co L₃-edge resonant inelastic x-ray scattering (RIXS) on bulk LaCoO₃ across the thermally-induced spin-state crossover around 100 K. Owing to a high energy resolution of 20 meV, we observe unambiguously the dispersion of the intermediate-spin (IS) excitations in the low temperature regime. Approaching the intermediate temperature regime, the IS excitations are damped and the bandwidth reduced. The observed behavior can be well described by a model of mobile IS excitons with strong attractive interaction, which we solve using dynamical mean-field theory for hard-core bosons. Our results provide a detailed mechanism of how HS and IS excitations interact to establish the physical properties of cobaltite perovskites.