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TT: Fachverband Tiefe Temperaturen

TT 7: Correlated Electrons: Spin Systems, Itinerant Magnets 1

TT 7.6: Talk

Monday, March 11, 2013, 10:45–11:00, H19

Z₂-vortex phase in a triangular-lattice Kitaev-Heisenberg model: Numerical simulations — Ioannis Rousochatzakis, Ulrich K. Rössler, Jeroen van den Brink, and •Maria Daghofer — IFW Dresden

We present numerical evidence for a Z₂-vortex phase in the triangular-lattice Kitaev-Heisenberg model. We performed unbiased Monte-Carlo simulations and found at least two incommensurate phases: One of them is dominated by three incommensurate ordering vectors, one for each spin component, S^x, S^y and S^z. This phase hosts localized defects that are similar to skyrmions, but are here identified as Z₂ vortices. The vortices are seen to form regular lattices that optimize their distance and whose lattice constant is determined by the incommensurate ordering vectors. For very large spin-orbit coupling, a different incommensurate phase emerges, where the symmetry between the three lattice directions (and spin components) is broken. One spin component dominates here and finite temperatures are characterized by nearly decoupled antiferromagnetic Ising chains, as in the square-lattice compass model. Connections to models for iridates will also be discussed.
[1] I. Rousochatzakis, U. K. Rössler, J. van den Brink, M. Daghofer, arXiv:1209.5895