Condensed Matter Theory Seminar | November 14, 14:00
A functional renormalization-group approach for frustrated quantum spin-systems
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.
FU Berlin
Seminar Room 03 - ETP
Contact: Simon Trebst