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TT: Tiefe Temperaturen
TT 11: Postersitzung II (Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen, Theorie: Systeme korrelierter Elektronen)
TT 11.30: Poster
Dienstag, 25. März 2003, 14:30–19:00, P2c, P2d
Electronic structure of the coupled-tetrahedra quantum spin systems Cu2Te2O5Br2 and Cu2Te2O5Cl2 — •Roser Valenti1, Tanusri Saha-Dasgupta2, Claudius Gros1, Helge Rosner3, and Peter Lemmens4 — 1Fakultät 7, Theoretische Physik, Universität des Saarlandes — 2S.N. Bose National Centre for Basic Sciences, JD Block, Sector 3,Salt Lake City, Kolkata 700098, India — 3MPI for Chemical Physics of Solids, Dresden — 4MPI for Solid State Research, Stuttgart
We present a comparative ab initio study of the electronic properties of the isostructural coupled-tetrahedra compounds Cu2Te2O5Br2 and Cu2Te2O5Cl2. A detailed investigation of the copper-copper interaction pathes reveals that the halogen-ions play an important role in the inter-tetrahedral couplings via X4-rings (X=Br, Cl). We find that, contrary to initial indications, both systems show a similar electronic behavior with long range exchange pathes mediated by the X4-rings.