Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 47: Correlated Electrons: Other Materials

TT 47.3: Vortrag

Mittwoch, 9. März 2016, 11:00–11:15, H23

Theoretical study of spin-state transition in LaCoO₃ using LDA+MLFT — •Evgeny Gorelov¹, Igor Krivenko², Michael Karolak³, and Alexander Lichtenstein^1,2 — ¹European XFEL GmbH Albert-Einstein-Ring 19, 22761 Hamburg, Germany — ²University of Hamburg, Jungiusstrasse 9, 20355 Hamburg, Germany — ³University of Würzburg, Sanderring 2, 97070 Würzburg, Germany

LaCoO₃ demonstrates variety of phase transitions due to competing interactions governing it’s electronic structure, including metal-to-insulator transition around T≈500 K and gradual spin-state transition around T≈80-120 K. In this work we focus on spin-state transition, and use theoretical approach of M. Haverkort, taking into account transition metal ion and it’s octahedral oxygen surrounding [1]. This approach allow us to calculate the resonant Co L_2,3 X-ray absorption spectra (XAS), using ab-initio calculated model parameters, i.e. nearest neighbors hopping matrix. The calculations are performed for experimental crystal structures for different temperatures in the range of 5-600 K [2]. In our calculations we include Co 3d orbitals with full Coulomb vertex, and five ligand orbitals, constructed from 2p orbitals of O atoms, forming the octahedra around Co ion. We discuss changes in the XAS spectra induced by thermal expansion of the lattice, as well as caused by change of electron temperature.
M. W. Haverkort, M. Zwierzycki, and O. K. Andersen,

PRB 85, 165113 (2012)
P. G. Radaelli and S.-W Cheong, PRB 66, 094408 (2002)