Regensburg 1998 – scientific programme
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TT: Tiefe Temperaturen
TT 24: Metall-Isolator-Übergang und Spin-Peierls-Systeme
TT 24.9: Talk
Friday, March 27, 1998, 11:30–11:45, H 19
Inelastic light scattering studies in the “spin-Peierls” compound α-NaV2O5 — •M. Fischer1, P. Lemmens1, G. Güntherodt1, M. Weiden2, R. Hauptmann2, C. Geibel2, and F. Steglich2 — 12. Physikalisches Institut, RWTH Aachen, Templergraben 55, 52056 Aachen — 2Max-Planck Institut f"ur chemische Physik fester Stoffe, 01187 Dresden
α-NaV2O5 is considered to be the second inorganic spin-Peierls compound with TSP= 34 K. Raman scattering studies on single crystalline samples of α-NaV2O5 were performed in a wide temperature range (5-300 K). Below TSP we observe several new modes, which we assign to zone-boundary folded phonon modes and magnetic bound states. The low-energy magnetic excitation spectrum shows striking differences to the one observed in CuGeO3. In addition to modes at 64 cm−1, at 103 cm−1 appearing for polarizations perpendicular to the chains, and an onset of a continuum at 130 cm−1, we also observe a sequence of modes with polarizations parallel to the chains. Moreover, the mode at 64 cm−1 and the continuum above 130 cm−1 appear also in crossed polarizations. These results are in disagreement with an interpretation of α-NaV2O5 as a simple one-dimensional spin-Peierls system. We therefore propose a different physical picture for the low temperature phase based on a dynamic two-dimensional dimer configuration.
Work supported by DFG through SFB 341 and BMBF Fkz 13N6586