Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 101: Correlated Electrons: Other Materials
TT 101.4: Vortrag
Donnerstag, 15. März 2018, 16:15–16:30, HFT-FT 101
The c-axis dimer and its electronic break-up: the insulator-to-metal transition in Ti2O3 — •chun-fu chang1, thomas c. koethe2, zhiwei hu1, jonas weinen1, stefano agrestini1, jan gegner2, holger ott2, giancarlo panaccione3, hua wu4, maurits w. haverkort5, holger roth2, alexander c. komarek1, francesco offi6, giulio monaco7, yen-fa liao8, ku-ding tsuei8, hong-ji lin8, chien-te chen8, arata tanaka9, and liu hao tjeng1 — 1MPI CPfS, Dresden, Germany — 2IOP II, Cologne, Germany — 3TASC Laboratory, Trieste, Italy — 4DOP, Shanghai, P.R. China — 5Institute for Theoretical Physics, Heidelberg, Germany — 6CNISM and DOS, Rome, Italy — 7ESRF, Grenoble, France — 8NSRRC, Hsinchu, Taiwan — 9DOQM, ADSM, Hiroshima, Japan
We report on our investigation of the electronic structure of Ti2O3 using (hard) x-ray photoelectron and soft x-ray absorption spectroscopy. From the distinct satellite structures in the spectra we have been able to establish unambiguously that the Ti-Ti c-axis dimer in the corundum crystal structure is electronically present and forms an (a1g)(a1g) molecular singlet in the low temperature insulating phase. Upon heating we observed a considerable spectral weight transfer to lower energies with orbital reconstruction. The insulator-metal transition may be viewed as a transition from a solid of isolated Ti-Ti molecules into a solid of electronically partially broken dimers where the Ti ions acquire additional hopping in the a-b plane via the egπ channel, the opening of which requires the consideration of the multiplet structure of the on-site Coulomb interaction.