Mott-Hubbard gap closure and structural phase transition in the oxyhalides TiOBr and TiOCl under pressure

C. A. Kuntscher, A. Pashkin, H. Hoffmann, S. Frank, M. Klemm, S. Horn, A. Schönleber, S. van Smaalen, M. Hanfland, S. Glawion, M. Sing, and R. Claessen
Phys. Rev. B 78, 035106 – Published 8 July 2008

Abstract

Pressure-dependent transmittance and reflectance spectra of TiOBr and TiOCl single crystals at room temperature suggest the closure of the Mott-Hubbard gap, i.e., the gap is filled with additional electronic states extending down to the far-infrared range. According to pressure-dependent x-ray powder-diffraction data, the gap closure coincides with a structural phase transition. The transition in TiOBr occurs at slightly lower pressure (p=14GPa) compared to TiOCl (p=16GPa) under hydrostatic conditions, which is discussed in terms of the chemical pressure effect. The results of pressure-dependent transmittance measurements on TiOBr at low temperatures reveal similar effects at 23 K, where the compound is in the spin-Peierls phase at ambient pressure.

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  • Received 7 April 2008

DOI:https://doi.org/10.1103/PhysRevB.78.035106

©2008 American Physical Society

Authors & Affiliations

C. A. Kuntscher*, A. Pashkin, H. Hoffmann, S. Frank, M. Klemm, and S. Horn

  • Experimentalphysik 2, Universität Augsburg, D-86135 Augsburg, Germany

A. Schönleber and S. van Smaalen

  • Laboratory of Crystallography, Universität Bayreuth, 95440 D-Bayreuth, Germany

M. Hanfland

  • European Synchrotron Radiation Facility, Boîte Postale 220, F-38043 Grenoble, France

S. Glawion, M. Sing, and R. Claessen

  • Experimentelle Physik 4, Universität Würzburg, 97074 D-Würzburg, Germany

  • *christine.kuntscher@physik.uni-augsburg.de

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Vol. 78, Iss. 3 — 15 July 2008

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