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TT: Fachverband Tiefe Temperaturen

TT 47: Poster Session Correlated Electrons 2

TT 47.15: Poster

Mittwoch, 18. März 2020, 15:00–19:00, P2/3OG

Hard-core bosonic dynamical mean-field study on melting of excitonic dispersion in LaCoO₃ — •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, 1040 Vienna, Austria — ²Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands — ³Akhiezer Institute for Theoretical Physics, NSC KIPT, Akademichna 1, 61108 Kharkiv, Ukraine — ⁴Department of Physics, Tohoku University, Aoba, Sendai 980-8578, Japan — ⁵European Synchrotron Radiation Facility, 71 Avenue des Martyrs, CS40220, F-38043 Grenoble Cedex 9, France — ⁶Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Praha 8, Czechia

We study excitonic nature of the spin-state transition in LaCoO₃. Based on Co L₃-edge resonant inelastic x-ray scattering (RIXS) data, we construct an effective bosonic model which describes (i) intermediate-spin (S=1, IS) excitons propagating on a low-spin (S=0) background and (ii) a high-spin (S=2, HS) state as tightly-bound two IS excitons. The effective model is solved at finite temperatures by means of hard-core bosonic dynamical mean-field theory (HB-DMFT). The RIXS data across the spin-state transition around 100K reveals melting of the IS excitonic dispersion. The HB-DMFT analysis of the RIXS data points out a novel picture of the HS state as bi-exciton dressed by virtual fluctuations HS↔IS+IS.