Possible structural transformation and enhanced magnetic fluctuations in exfoliated α-RuCl3

We present Raman spectroscopy experiments on exfoliated alpha-RuCl3, from tens of nm thick down to single layers. Besides unexpectedly finding this material to be air stable, in the thinnest layers we observe the appearance with decreasing temperature of a symmetry-forbidden mode in crossed polarization, along with an anomalous broadening of a mode at 164 cm(-1) that is known to couple to a continuum of magnetic excitations. This may be due to an enhancement of magnetic fluctuations and evidence for a distorted honeycomb lattice in single- and bilayer samples.