Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 18: Metall-Isolator-Überg
änge in Quantensystemen I
TT 18.7: Vortrag
Donnerstag, 27. März 2003, 16:15–16:30, HSZ304
Broadband dielectric and optical spectroscopy of LaTiO3 — •T. Rudolf, P. Lunkenheimer, and A. Loidl — Universität Augsburg, Institut für Physik, Universitätsstr. 2, 86135 Augsburg
The perovskite-like LaTiO3 is an antiferromagnetic Mott-Hubbard insulator [1]; recently a scenario of an orbital liquid was discussed for this material. We measured dielectric permittivity, ac-conductivity and optical conductivity of single-crystalline LaTiO3 in the range of 1.4 K to 300 K by dielectric spectroscopy (frequencies 0.01 Hz - 1 GHz) and Fourier-Transform-Spectroscopy (1.5 - 750 THz). The phonon spectra, revealing 14 modes, were investigated in detail. The optical gap was analyzed comparing the experimental data with theoretical predictions. The ac-conductivity at ν<2 GHz follows the Universal Dielectric Response indicating hopping conduction of localized charge carriers. Combining the dielectric and optic results reveals an additional high-frequency superlinear power law ("second universality"). From the low-frequency optical spectra (frequencies < 1 eV ≃ 240 THz) we speculate about the occurrence of a quasi-particle peak, which is expected close to a metal-to-insulator transition due to electronic correlations.
[1] V. Fritsch, J. Hemberger, M.V. Eremin, H.-A. Krug von Nidda, F. Lichtenberg, R. Wehn, and A. Loidl, Phys. Rev. B 65, 212405 (2002).