Angle resolved Raman Spectroscopy of RuCl3 thin layers

Alpha-RuCl3 is a layered candidate material to host the Kitaev quantum spin liquid. However, the magnetic ground state of RuCl3 exhibits a zigzag antiferromagnetic (AFM) order, suggesting deviations from the pure Kitaev model. The in-plane zigzag AFM state corresponds to the orientation of the honeycomb lattice structure, whereas a method to easily determine the crystallographic axes for the exfoliated RuCl3 has not been established. We used angle resolved Raman spectroscopy to determine the in-plane crystal axes of exfoliated RuCl3. Samples were rotated in the xy-plane of the honeycomb lattice, and Raman spectra were taken in cross and parallel polarization configurations. By monitoring the Raman intensity from one of the Ag modes as a function of the rotational angle, we can determine the b-axis of the RuCl3 crystal. Our study provides a nondestructive and convenient method for determining the crystal orientation of RuCl3.