Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 45: Correlated Electrons: Poster Session

TT 45.70: Poster

Donnerstag, 29. März 2012, 15:00–19:00, Poster B

Cs₂CuCl_4−xBr_x: perspectives of experimentally tunable frustration in a triangular lattice — •Kateryna Foyevtsova, Ingo Opahle, Harald O. Jeschke, and Roser Valentí — Institut für Theoretische Physik, Goethe-Universität Frankfurt, Frankfurt am Main, Germany

Frustrated antiferromagnets Cs₂CuCl₄ and Cs₂CuBr₄ with an underlying triangular lattice demonstrate rich magnetic phase diagrams, where one finds a spin-liquid phase for Cs₂CuCl₄ and quantum fluctuation stabilized magnetization plateaux for Cs₂CuBr₄. The magnetism of Cs₂CuCl₄ and Cs₂CuBr₄ might be understood in terms of the triangular Heisenberg model with different degrees of frustration: J′/J ∼ 0.3 for Cs₂CuCl₄ and J′/J ∼ 0.7 for Cs₂CuBr₄. Recently, mixed systems Cs₂CuCl_4−xBr_x have been synthesized for a dense mesh of x values from 0 to 4, which suggests that it might be possible to tune the J′/J ratio by varying x. We apply the density functional theory to study the crystal and electronic structures of some members of the Cs₂CuCl_4−xBr_x series. In particular, we are interested in the microscopic equilibrium distribution of the substituted halogen atoms which affects the spin exchange couplings J and J′. We also discuss the two structural phases – orthorhombic and tetragonal – that might emerge during crystal growth, depending on the growth conditions.