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TT: Fachverband Tiefe Temperaturen

TT 28: Correlated Electrons: Low-dimensional Systems - Materials 2

TT 28.9: Talk

Wednesday, March 28, 2012, 17:15–17:30, H 0104

Analysis of the temperature dependence of the structural and electronic properties of the spin liquid candidate κ-(BEDT-TTF)₂Cu₂(CN)₃ — •Harald O. Jeschke¹, Mariano de Souza², Rudra Sekhar Manna², Michael Lang², Roser Valentí¹, and John A. Schlueter³ — ¹Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany — ²Physikalisches Institut, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany — ³Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States

The interplay of the effects of electronic correlations, low dimensionality and spin frustration in the organic charge transfer salt κ-(BEDT-TTF)₂Cu₂(CN)₃ is of great interest experimentally as well as theoretically. Besides the spin liquid property at very low temperatures, the material has interesting anomalies at 6K, 60K and 150K. Even though the structure of the material has been determined several times over the past 20 years, complete structural data are only available at room temperature. In our work, we precisely determine the structure at 300K, 250K, 200K, 150K, 100K, 20K and 5K. We analyze the structures using density functional theory and tight binding methods. We show that the triangular lattice Hubbard Hamiltonian parameters are temperature dependent, with the interaction strength increasing with decreasing temperature and with the frustration going through a minimum at 150 K. Our results point to the fact that the experimental determination of structures at various temperatures may be important for realistic many-body theoretical investigations of complex materials.