Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 9: Correlated Electrons: Metal-Insulator Transition 1
TT 9.5: Talk
Monday, March 23, 2009, 15:00–15:15, HSZ 03
Drastic Spectral Weight Transfer across the Metal-Insulator Transition in Ca2−xSrxRuO4 Revealed by Soft-X-ray Photoemission — •H. Fujiwara1, Z. Hu1, T. C. Koethe1, A. Hendricks1, M. Zell1, N. B. Brookes2, S. Nakatsuji3, and L. H. Tjeng1 — 1II. Physikalisches Institut, Universität zu Köln, Köln, Germany — 2European Synchrotron Radiation Facility, Grenoble, France — 3Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
The layered Ca2−xSrxRuO4 system shows a very rich phase diagram as a function of the x-composition, temperature and magnetic field. Particularly fascinating is the electronic structure in the range of 0<x<0.2 where the metal-insulator transition (MIT) takes place at a continuously decreasing temperature with x getting closer to 0.2. This transition is accompanied by a drop in the resistivity of several orders of magnitude, comparable to that in V2O3 and VO2. In order to reveal the mechanism of the MIT in Ca2−xSrxRuO4, we have carried out a photoemission study with hν = 700 eV to obtain reasonable sensitivity to the Ru 4d spectral weight. We have found that there is a dramatic transfer of the spectral weight across the MIT. Since x-ray absorption spectroscopy has shown that the orbital occupation of the three t2g bands changes significantly across the MIT, as is the case also in the MITs of V2O3 [1] and VO2 [2], our results suggest the crucial role of the orbital switching for the MIT of Ca2−xSrxRuO4.
[1] J.-H. Park, et al., Phys. Rev. B 61, 11506 (2000).
[2] M. W. Haverkort, et al., Phys. Rev. Lett. 95, 196404 (2005).