Unconventional spin dynamics in the honeycomb-lattice material $\alpha$-RuCl$_3$: high-field ESR studies

Understand

We present high-field electron spin resonance (ESR) studies of the honeycomb-lattice material $\alpha$-RuCl$_3$, a prime candidate to exhibit Kitaev physics.

• Two modes of antiferromagnetic resonance were detected in the zigzag ordered phase, with magnetic field applied in the $ab$ plane.
• A very rich excitation spectrum was observed in the field-induced quantum paramagnetic phase.
• The obtained data are compared with results of recent numerical calculations, strongly suggesting a very unconventional multiparticle character of the spin dynamics in $\alpha$-RuCl$_3$.