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arXiv · 1404.4523

Quantum fluctuations in anisotropic triangular lattices with ferro- and antiferromagnetic exchange

Burkhard Schmidt·Peter Thalmeier
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Abstract

The Heisenberg model on a triangular lattice is a prime example for a geometrically frustrated spin system. However most experimentally accessible compounds have spatially anisotropic exchange interactions. As a function of this anisotropy, ground states with different magnetic properties can be realized. Motivated by recent experimental findings on Cs$_{2}$CuCl$_{4-x}$Br$_{x}$, we discuss the full phase diagram of the anisotropic model with two exchange constants $J_{1}$ and $J_{2}$, including possible ferromagnetic exchange. Furthermore a comparison with the related square lattice model is carried out. We discuss the zero-temperature phase diagram, ordering vector, ground-state energy, and ordered moment on a classical level and investigate the effect of quantum fluctuations within the framework of spin-wave theory. The field dependence of the ordered moment is shown to be nonmonotonic with field and control parameter.

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Burkhard Schmidt, Peter Thalmeier. 2014-04-17. Quantum fluctuations in anisotropic triangular lattices with ferro- and antiferromagnetic exchange. https://doi.org/10.1103/physrevb.89.184402

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