Possible Structural Transformation and Enhanced Magnetic Fluctuations in Exfoliated $\alpha$-RuCl$_3$

TL;DR

This study uses Raman spectroscopy to investigate exfoliated $ ext{α-RuCl}_3$ flakes, revealing structural and magnetic fluctuation changes in ultra-thin layers, including a symmetry-forbidden mode and broadening of a magnetic mode.

Contribution

First Raman analysis of exfoliated $ ext{α-RuCl}_3$ layers showing structural transformation and magnetic fluctuation enhancement in monolayer and bilayer samples.

Findings

Air stability of exfoliated $ ext{α-RuCl}_3$

Appearance of symmetry-forbidden mode in thin layers at low temperature

Broadening of magnetic excitation mode at 164 cm$^{-1}$

Abstract

We present initial Raman spectroscopy experiments on exfoliated flakes of $\alpha$-RuCl$_3$, 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 bi-layer samples.