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Berlin 2024 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 27: Correlated Electrons: Other Materials

TT 27.1: Vortrag

Dienstag, 19. März 2024, 09:30–09:45, H 3010

Orbital imaging in VO2 across the insulator to metal transition — •Paulius Dolmantas1, Chun-Fu Chang1, Martin Sundermann1,2, Hlynur Gretarsson1,2, Marcus Schmidt1, Maurits W. Haverkort3, Arata Tanaka4, and L.H. Tjeng11Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany — 2DESY/PETRA-III, Hamburg, Germany — 3Institute for Theoretical Physics, Heidelberg University, Heidelberg, Germany — 4Department of Quantum Matter, Hiroshima University, Japan

Transition metal oxide VO2 undergoes an metal to insulator transition (MIT) at 340 K from insulating monoclinic phase to a metallic rutile phase. For many decades this MIT in VO2 has been extensively studied and still is a subject of debate whether it is driven by Mott-Hubbard mechanism or Peierls mechanism. X-ray absorption measurements together with multiplet theory calculations indicated orbital redistribution from almost isotropic in the metallic phase at 373 K to strongly σ orbital polarized at 300 K, suggesting a collaborative Mott-Peierls transition mechanism. Using recently developed X-ray-based orbital-imaging method, we experimentally and directly observe an orbital redistribution across the transition, no theoretical calculations involved. We find that at 20K VO2 has indeed mainly σ orbital character in the insulating phase. The σ orbital polarization vanishes above the transition. This direct observation of the orbital redistribution across a MIT shall have significant implications for ab-initio modeling of metal-insulator transitions.

Keywords: Complex Oxides; VO2; Orbital imaging; Phase transitions

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