Raman spectra resolve two pressure-driven transitions in α-RuCl₃
As pressure increased, the layers first changed their stacking arrangement and then ruthenium atoms formed pairs within a layer.
Gaomin Li and colleagues compressed α-RuCl₃ crystals in a diamond anvil cell and followed their room-temperature Raman spectra. New modes appeared near 1.1 GPa. Together with second-harmonic measurements, these modes indicated a change in layer stacking.
Near 1.7 GPa a ruthenium vibration softened and split, consistent with atoms forming pairs within the layers. The authors linked this second transition to the collapse of the Mott insulating state. Liyuan Zhang co-authored the paper.