Electronic structure and correlation in -TiO and -TiO studied by hard X-ray photoelectron spectroscopy

小林 啓介*; 田口 宗孝*; 小畠 雅明; 田中 健司*; 所 裕子*; 大門 寛*; 岡根 哲夫; 山上 浩志; 池永 英司*; 大越 慎一*

Physical Review B, 95(8), p.085133_1 - 085133_7, 2017/02

AA2017-0038.pdf:0.98MB

https://doi.org/10.1103/PhysRevB.95.085133

We have conducted hard X-ray photoelectron spectroscopy investigations of the electronic structure changes and electron correlation phenomena which take place upon the photoinduced reversible phase transition between - and -TiO. From valence band spectra of - and -TiO, we have identified the bipolaron caused by the -type bonding of orbitals in -TiO and the stacking between the orbitals between different Ti sites in -TiO, previously predicted by calculations. On the other hand, the Ti and Ti core level spectra exhibit nonlocal screening satellite features, which are typical spectroscopic signs of strong electron correlation in the coherent Ti states. Correlation in the valence band also manifests to reduce the plasmon energy, which results in an enhancement of the valence electron mass by a factor of 2.7.