Regensburg 1998 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Postersitzung III: Spin-Peierls-Systeme, Metall-Isolator-Übergang, Lokalisierung; SL: Theorie; Quantenflüssigkeiten und -kristalle; Amorphe Materialien, Tunnelsysteme; Borcarbide, Fullerene, konventionelle SL; SL dünner Filme; Experimentiertechniken

TT 21.29: Poster

Donnerstag, 26. März 1998, 15:00–18:30, D

Three-Magnon Light Scattering in CuGeO₃ — •G. Els¹, P.H.M. van Loosdrecht¹, P. Lemmens¹, H. Vonberg¹, G. Güntherodt¹, G.S. Uhrig², O. Fujita³, J. Akimitsu³, G. Dhalenne⁴, and A. Revcolevschi⁴ — ¹2. Phys. Inst., RWTH Aachen, 52056 Aachen, Germany — ²Inst. für Theor. Phys., Universität Köln, 50937 Köln, Germany — ³Dep. of Physics, Aoyama Gakuin University, Tokyo 157, Japan — ⁴Laboratoire de Chimie des Solides, Université de Paris-Sud, 91405 Orsay, France

Brillouin light scattering experiments have been performed on CuGeO₃ single crystals as a function of temperature (2K<T<20K), magnetic field (0T<H<6T), and light polarization. Below the spin-Peierls temperature T_SP a thermally activated weak shoulder at roughly 18 cm⁻¹ is observed on the low energy side of the 30-cm⁻¹ singlet bound state (SBS). The position of this shoulder has a similar temperature dependence as that of the SBS. Therefore this shoulder is attributed to transitions between magne tically excited states of the dimerized phase [1]. Within a light scattering theory, based on the exchange scattering mechanism, the appearance of this shoulder can be explained by a novel three-magnon scattering process. This process describes transitions between the well-defined triplet branch (one-magnon) and the two-magnon continuum under spin and momentum conservation.

Work supported by DFG through SFB 341 and BMBF Fkz. 13N6586

[1] G. Bouzerar, A. P. Kampf, F. Schönfeld, preprint cond-mat 9701176.