Lattice dynamics and phase transition in CrI_3 single crystals

摘要

The vibrational properties of CrI_3 single crystals were investigated using Raman spectroscopy and were analyzed with respect to the changes of the crystal structure. All but one mode are observed for both the low-temperature R3 and the high-temperature C2/m phase. For all observed modes the energies and symmetries are in good agreement with DFT calculations. The symmetry of a single layer was identified as p31/m. In contrast to previous studies we observe the transition from the R3 to the C2/m phase at 180 K and find no evidence for coexistence of both phases over a wide temperature range.