Raman scattering has been employed to investigate lattice and magnetic excitations of the honeycomb Kitaev material α-RuCl3 and its Heisenberg counterpart CrCl3. Our phonon Raman spectra give evidence for a first-order structural transition from a monoclinic to a rhombohedral structure for both compounds. Significantly, only α-RuCl3 features a large thermal hysteresis, consistent with the formation of a wide phase of coexistence. In the related temperature interval of 70−170 K, we observe a hysteretic behavior of magnetic excitations as well. The stronger magnetic response in the rhombohedral compared to the monoclinic phase evidences a coupling between the crystallographic structure and low-energy magnetic response. Our results demonstrate that the Kitaev magnetism concomitant with fractionalized excitations is susceptible to small variations of bonding geometry.
@article{arxiv.1705.01312,
title = {Relation between Kitaev magnetism and structure in $\alpha$-RuCl$_3$},
author = {A. Glamazda and P. Lemmens and S. -H. Do and Y. S. Kwon and K. -Y. Choi},
journal= {arXiv preprint arXiv:1705.01312},
year = {2017}
}