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arXiv · 1209.5895

Z_2-vortex lattice in the ground state of the triangular Kitaev-Heisenberg model

Ioannis Rousochatzakis·Ulrich K. Rössler·Jeroen van den Brink·Maria Daghofer
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Abstract

The triangular-lattice Heisenberg antiferromagnet (HAF) is known to carry topological Z_2 vortex excitations which form a gas at finite temperatures. Here we show that the spin-orbit interaction, introduced via a Kitaev term in the exchange Hamiltonian, condenses these vortices into a triangular $Z_2$ vortex crystal at zero temperature. The cores of the Z_2 vortices show abrupt, soliton-like magnetization modulations and arise by a special intertwining of three honeycomb superstructures of ferromagnetic domains, one for each of the three sublattices of the 120-degree state of the pure HAF. This is a new example of a nucleation transition, analogous to the spontaneous formation of magnetic domains, Abrikosov vortices in type-II syperconductors, blue phases in cholesteric liquid crystals, and skyrmions in chiral helimagnets. As the mechanism relies on the interplay of geometric frustration and spin-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.

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Ioannis Rousochatzakis, Ulrich K. Rössler, Jeroen van den Brink, Maria Daghofer. 2012-09-26. Z_2-vortex lattice in the ground state of the triangular Kitaev-Heisenberg model. https://doi.org/10.1103/physrevb.93.104417

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