Spontaneous Spatial Inversion Symmetry Breaking and Spin Hall Effect in a Spin-ice Double-exchange Model on a Pyrochlore Lattice

TL;DR

This study reveals that a spin-ice double-exchange model on a pyrochlore lattice spontaneously forms tetrahedral spin clusters that break spatial inversion symmetry and exhibit a nonzero spin Hall effect, independent of spin-orbit coupling.

Contribution

It demonstrates the emergence of a spin Hall effect driven by intersite-multipole order in a spin-ice model without relying on spin-orbit interaction.

Findings

Formation of tetrahedral spin clusters breaks inversion symmetry.

Nonzero spin Hall conductivity observed in the spin-cluster phase.

Spin Hall effect arises from intersite-multipole order, not spin-orbit coupling.

Abstract

A formation of tetrahedral spin clusters is discovered by Monte Carlo simulation for a spin-ice type double-exchange model on a pyrochlore lattice. The spin-cluster phase is magnetically disordered, but breaks spatial inversion symmetry spontaneously by developing noncoplanar four-spin molecules periodically on the pyrochlore lattice. We find that the system exhibits a nonzero spin Hall conductivity in the spin-cluster phase. The result suggests that an intersite-multipole order induces the unconventional spin Hall state without the spin-orbit interaction.