Regensburg 2025 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 52: Nickelates and Other Complex Oxides
TT 52.7: Talk
Friday, March 21, 2025, 11:00–11:15, H31
Localized Ti-4s molecular orbitals and correlated 3d states in the bad metal TiOx — •Daisuke Takegami1,2, Anna Melendez-Sans2, Takashi Miyoshino1, Ryo Nakamura1, Miguel Ferreira-Carvalho3,2, Georg Poelchen2, Chun-Fu Chang2, Masato Yoshimura4, Ku-Ding Tsuei4, Haruka Matsumoto5, Asuka Yanagida5, Takuro Katsufuji5, Liu Hao Tjeng2, and Takashi Mizokawa1 — 1Department of Applied Physics, Waseda University, Japan — 2Max Planck Institute for Chemical Physics of Solids, Germany — 3Institute of Physics II, University of Cologne, Germany — 4National Synchrotron Radiation Research Center, Taiwan — 5Department of Physics, Waseda University, Japan
We have investigated the electronic structure of the rocksalt TiOx system using polarizationdependent hard x-ray photoelectron spectroscopy. The spectra showed a vanishingly small intensity at the Fermi level, classifying TiOx as a bad metal. With the main spectral features attributed to the Ti2+ 3d2 configuration, we were able to detect spectroscopically also the co-existence of both Ti and O vacancies. The presence of Ti3+ states were identified. It was a surprise not to find signs for Ti1+ entities. Instead a sharp occupied state of Ti 4s origin was unveiled in the valence band, which gave evidence that localized Ti-4s-based molecular orbitals are formed around the O vacancies. Our findings suggest that a defect free and stoichiometric TiO would have been a strongly correlated a Mott-Hubbard insulator, and that the 4s is an important degree of freedom for low-valent 3d materials.
Keywords: TiO; HAXPES; Vacancies; Mott-Hubbard; 4s