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TT: Tiefe Temperaturen

TT 14: Postersitzung II: Korrelierte Systeme(1-40), Theorie der Supraleitung(41-50), Metall-Isolator-Übergang, Lokalisierung(51-66), Niederdimensionale Systeme, Quantenhalleffekt(67-80), Pinning, kritische Ströme und Vortexdynamik(81-93), HTSL-Drähte und -Bänder(94-98), Massive HTSL(99-104), supraleitende Borkarbide(105-109)

TT 14.78: Poster

Mittwoch, 19. März 1997, 15:00–18:30, Z1

Spin-Peierls transition in CuGeO₃ investigated by Brillouin
spectroscopy — •G. Els¹, P. Lemmens¹, H. Vonberg¹, G. Güntherodt¹, M. Udagawa², O. Fujita³, and J. Akimitsu³ — ¹2. Physikalisches Institut, RWTH Aachen, 52056 Aachen — ²Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739, Japan — ³Department of Physics, Aoyama Gakuin University, 6-16-1 Chitosedai, Setagaya-ku, Tokyo, Japan

Brillouin light scattering has been performed in a frequency range from 3 to 3000 GHz. The longitudinal acoustic phonon mode along the b direction is anomalously close to the transverse mode. At 5K an asymmetric excitation could be observed at 920 GHz (3.8 meV) which is due to two-magnon scattering from the spin-Peierls gap at k=[0,1,1/2]. By increasing the temperature from 5K up to T_SP the two-magnon peak softens and decreases in intensity. At the same time a shoulder emerges at the low frequency side of this excitation and is well established at 9K near 530 GHz (2.2 meV). This corresponds to the energy of a one-magnon excitation at k=[0,1,1/2]. The temperature dependence of this excitation gives evidence for a fluctuation induced scattering process, yielding k-conservation. Above 13 K both peaks disappear in a continuous background which decreases by raising the temperature up to 17K.
Work supported by DFG through SFB 341 and BMBF Fkz. 13N6586