paper

Hedgehog lattice and field-induced chirality in breathing-pyrochlore Heisenberg antiferromagnets

arXiv:2206.03707 · doi:10.1103/PhysRevB.106.064412

Abstract

We theoretically investigate a - classical Heisenberg model on the breathing pyrochlore lattice, where the nearest-neighbor (NN) exchange interactions for small and large tetrahedra, and , take different values due to the breathing bond-alternation and is the third NN antiferromagnetic interaction along the bond direction. It is found by means of Monte Carlo simulations that for large , a hedgehog lattice, a three-dimensional periodic array of magnetic monopoles and antimonopoles, emerges in the form of a quadruple- state characterized by the ordering vector of , being irrespective of the signs of and/or as long as . It is also found that in an applied magnetic field, there appear six quadruple- states depending on the values of and , among which three phases including the in-field hedgehog-lattice state exhibit nonzero total chirality $\mbox{\boldmath $χ$}^{\rm T}$ associated with the anomalous Hall effect of chirality origin. In the remaining two chiral phases, which are realized in the presence of ferromagnetic and/or , the spin structure is not topologically nontrivial, in spite of the fact that $\mbox{\boldmath $χ$}^{\rm T} \neq 0$. The role of the topological objects of the monopoles in $\mbox{\boldmath $χ$}^{\rm T}$ is also discussed.

21 pages, 20 figures

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