Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 47: Poster Session Correlated Electrons 2

TT 47.11: Poster

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

Electronic structure and dynamical properties of KO2 — •Dorota Gotfryd1,2, Olga Sikora3, Andrzej Ptok3, Andrzej M. Oles2,4, Krzysztof Wohlfeld1, and Przemyslaw Piekarz31Faculty of Physics, University of Warsaw, Pasteura 5, PL-02093 Warsaw, Poland — 2Institute of Physics, Jagiellonian University, Lojasiewicza 11, PL-30348 Krakow, Poland — 3Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Krakow, Poland — 4Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany

Here we investigate the possible mechanisms behind the insulating properties of the strongly correlated superoxide KO2. The intermediate monoclinic C2/c phase with O2 molecules rotated by about 20 deg from the high-temperature tetragonal structure reported in experiments is here examined by means of density functional theory and lattice dynamics. We identify a soft phonon leading to the new stable distorted phase of C2/c symmetry and analyse its structural properties. Comparison of the electronic structure of KO2 in the tetragonal and monoclinic phases reveals the insulating mechanism in the monoclinic phase: while only the joint efforts of large on-site Coulomb and small spin-orbit interactions are able to open a small charge gap in the tetragonal phase, in the monoclinic phase perturbing GGA+U by the small spin-orbit coupling moves KO2 from weak to strong Mott-insulator regime. This indicates an important role of the interplay between Coulomb and on-site spin-orbit interactions as well as pronounced lattice distortions in formation of the insulating phase.

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