Using spin-orbit heavy metals as a probe for emergent phases in a honeycomb insulator

Materials with 5d and 4d orbitals host a plethora of intriguing properties stemming from the competition between different energy scale such as spin-orbit coupling, crystal-field energy, and exchange interactions. The intricate interplay between these interactions lead to frustration in the material and potentially to a realization of the Quantum Spin Liquid (QSL) state.
New methods to measure collective excitations are critical to the understanding and identification of spin liquids. By coupling a correlated magnetic insulator with frustrated interactions to a heavy metal with strong spin-orbit coupling, we use the spin-Hall effect to study the magnetism of the insulating material. Our measurements point to the presence of collective modes stemming from magnetic degrees of freedom, without evidence of symmetry breaking. We discuss how these techniques can be generalized to other exotic magnetic insulators.