Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 5: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 1 (jointly with MA)
TT 5.8: Vortrag
Montag, 16. März 2015, 11:30–11:45, H 0110
Z2-vortex lattice in the ground state of Kitaev-Heisenberg models — •Maria Daghofer1, Ioannis Rousochatzakis2, Ulrich K Rössler3, and Jeroen van den Brink3 — 1nstitut für Funktionelle Materie und Quantentechnologien, Universität Stuttgart — 2Max-Planck-Institut für Physik komplexer Systeme, Dresden — 3IFW Dresden, Dresden
In geometrically frustrated magnets, the strongly competing interactions between spins often suppress simple magnetic ordering patterns and clear space for new states of matter supporting rather exotic excitations, for instance, magnetic monopoles as topological excitations of spin-ice states on pyrochlore lattices. The triangular-lattice Heisenberg antiferromagnet also carries topological excitations, Z2 vortices, which form a Z2-vortex gas at finite temperatures. Here we show that spin-orbit interaction, introduced via a Kitaev term in the exchange Hamiltonian, causes the vortices to condense into a hexagonal superlattice at zero temperature. This is a new example of a nucleation transition, analogous to the Abrikosov vortex lattices in type-II superconductors, the blue phases in cholesteric liquid crystals, and the skyrmionic lattices observed in B20 chiral helimagnets. As the mechanism relies on the interplay of geometric frustration and orbital anisotropies, such vortex mesophases can materialize as a ground-state property in spin-orbit coupled correlated systems with nearly hexagonal topology, as in triangular or strongly frustrated honeycomb iridates.