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TT: Tiefe Temperaturen
TT 19: Correlated Electrons: Low-dimensional Materials
TT 19.4: Vortrag
Dienstag, 28. März 2006, 14:45–15:00, HSZ 301
Optical response of the low-dimensional insulator TiOCl under pressure — •S. Frank1, A. Pashkin1, C. A. Kuntscher1, M. Hoinkis2,3, M. Klemm2, M. Sing3, S. Horn2, and R. Claessen3 — 11.Physikalisches Institut, Universität Stuttgart, Germany — 2Experimentalphysik 2, Universität Augsburg, Germany — 3Experimentelle Physik 4, Universität Würzburg, Germany
The role of lattice, spin, and orbital degrees of freedom for the properties of the low-dimensional Mott insulator TiOCl is currently under debate. Upon cooling, the compound undergoes a transition to a non-magnetic ground state, most probably a spin-Peierls state. The role of the orbital degree of freedom is much less clear: The occurrence of a second phase transition was discussed in terms of strong orbital fluctuation; this picture was questioned by transmission measurements, showing strong absorption features which were interpreted in terms of transitions between the crystal field-split Ti t2g levels [1]. To obtain more information on the orbital excitations in TiOCl and to add new facets to its properties, we studied the polarization-dependent optical response as a function of pressure. The measurements were performed over a broad frequency range (mid-infrared to visible) on very thin crystals, which allowed to determine the position and lineshape of the absorption features as a function of pressure. We also discuss the possibility of a pressure-induced phase transition.
Supported by the DFG, Emmy Noether-program.
[1] R. Rückamp et al., Phys. Rev. Lett. 95, 097203 (2005)