Unconventional spin dynamics in the honeycomb-lattice material α − RuCl 3 : High-field electron spin resonance studies

The honeycomb-lattice material $\ensuremath{\alpha}$-RuCl${}_{3}$ is a prime candidate for exhibiting Kitaev spin-liquid physics. Here, the authors employ high-field electron spin resonance spectroscopy to probe its spin dynamics across different regions of the phase diagram. Apart from two modes of antiferromagnetic resonance in the zigzag-ordered phase, a rich excitation spectrum was observed in the field-induced quantum disordered state. The authors compare their observations with results of recent numerical calculations, revealing a complex multiparticle nature of magnetic excitations in the field-induced phase.