Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 31: Correlated Electrons - Low-dimensional Materials I

TT 31.7: Vortrag

Dienstag, 8. März 2005, 15:30–15:45, TU H2053

Infrared properties of the quasi-one-dimensional superconductor β-Na_0.33V₂O₅ under pressure — •C. A. Kuntscher¹, S. Frank¹, I. Loa², K. Syassen², T. Yamauchi³, and Y. Ueda³ — ¹1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany — ²Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart, Germany — ³Institute for Solid State Physics, University of Tokyo, Tokyo, Japan

At ambient pressure β-Na_0.33V₂O₅ shows a quasi-one-dimensional metallic character at room temperature, which can be explained by its highly anisotropic crystal structure consisting of chains and ladders of VO₆ octahedra and chains of VO₅ square pyramids. Upon cooling it undergoes a metal-insulator transition at 135 K due to charge ordering on the V sites. The pressure-temperature phase diagram of β-Na_0.33V₂O₅ is remarkable, since it shows a superconducting phase for pressures higher than 7 GPa in direct vicinity to the charge-ordered phase [1]. The mechanism of the observed superconductivity and its relation to the charge ordering is not clear. Besides, electron-phonon interaction seems to play a role as well, influencing the conduction mechanism.

We carried out polarization-dependent reflectivity measurements on β-Na_0.33V₂O₅ at room temperature as a function of pressure (<20 GPa). The results are discussed in terms of the conduction mechanism, pressure-induced structural changes, and charge ordering/redistribution. Supported by the DFG, Emmy Noether-program.

[1] T. Yamauchi, Y. Ueda, and N. Mori, Phys. Rev. Lett. 89, 057002 (2002).