Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 11: Postersitzung II (Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen, Theorie: Systeme korrelierter Elektronen)
TT 11.20: Poster
Dienstag, 25. März 2003, 14:30–19:00, P2c, P2d
Spectroscopic investigation of the Spin-Peierls-like instability in TiOCl — •P. Lemmens1,2, K.-Y. Choi2, T. Sahaoui2, A. Seidel3, and F.C. Chou3 — 1MPI for Solid State Research, D-70569 Stuttgart — 22. Physikalisches Institut, D-52056 RWTH Aachen — 3Center for Material Science and Engineering, MIT, Cambridge, MA 02139, USA
We present a Raman light scattering study of the layered titanium oxyhalide TiOCl. In this system LDA+U calculations propose the formation of S=1/2 Heisenberg chains by a direct overlap of ordered t2g orbitals of Ti3+ ions [1,2]. Experimentally, a broad maximum is observed in the high temperature magnetic susceptibility consistent with an afm coupling of J=660 K and a sudden decrease for temperatures below TC=100 K. Using Raman light scattering we studied excitations of the phonon system as well as high energy scattering attributed to electronic/magnetic degrees of freedom. The observed phonon anomalies point to strong dimer fluctuations. The scattering selection rules of the signals in the high-energy sector are consistent with the theoretical model. However, the line-shape of this scattering does not follow the Loudon-Fleury scenario of two-magnon scattering. We propose a novel interplay of orbital and spin excitations as the origin of this scattering. Work supported by DFG SPP1073
[1] A. Seidel, C.A. Marianetti, F.C. Chou, G. Ceder, P.A. Lee, cond-mat/0206374 (2002).
[2] A. Seidel and P.A. Lee, cond-mat/0212199 (2002).