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We apply the functional renormalization group (FRG) method to describe ground state properties of frustrated spin-1/2 systems on two-dimensional lattices. In order to be able to use this technique we rewrite the spin operators in terms of pseudo fermions. The resulting fermionic model is then treated via FRG, which manages to sum up diagrammatic contributions in different interaction channels in infinite order. Calculating the magnetic spin susceptibility we determine the ground state phase diagrams of various frustrated spin systems. Thereby, we discuss models such as the J1-J2 Heisenberg model on the square lattice and the Kagome Heisenberg model. A specific focus will be on the iridate compound Li_2IrO_3, where experiments suggest a magnetically ordered ground state of incommensurate spiral type. Applying our FRG technique to an extended Heisenberg-Kitaev model we are able to develop a microscopic scenario for the exchange interactions in this compound, explaining the experimental findings.

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Johannes Reuther, FU Berlin
Seminar Room 03 - ETP
Contact: Simon Trebst