Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 34: Correlated Electrons: Metal-Insulator Transition 2

TT 34.7: Talk

Thursday, February 28, 2008, 15:45–16:00, H 2053

Spectral weight distribution of d¹ Mott insulators LaTiO₃ and YTiO₃ — H. Roth¹, •T.C. Koethe¹, Hua Wu¹, Z. Hu¹, A. Hendricks¹, J. Gegner¹, M.W. Haverkort¹, T. Lorenz¹, J.C. Cezar², N.B. Brookes², I.S. Elfimov³, G.A. Sawatzky³, and L.H. Tjeng¹ — ¹II.Physikalisches Institut Universität zu Köln — ²European Synchrotron Radiation Facility (ESRF), BP 220, 38043 Grenoble Cedex, France — ³Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, Canada, V6T 1Z1

We have utilized bulk-sensitive photoelectron spectroscopy to study the valence band spectral weight distribution of d¹ Mott insulators LaTiO₃ and YTiO₃. We observed appreciable differences in the spectra, reflecting the difference in the one-electron band width. We also found that the Ti 3d spectra of both materials are much broader than the occupied 3d bands calculated by band theories. The mean-field inclusion of the Hubbard U explains the band gap but produces even narrower bands, indicating the complete breakdown of standard mean-field theories in describing excitation spectra. We associate the observed spectra with the propagation of a hole in a system with surprisingly well suppressed charge fluctuations thereby showing characteristics of a t-J model.