Pressure-Induced Structural Phase Transition and Enhanced Interlayer Coupling in Two-Dimensional Ferromagnet CrSiTe 3 .

The two-dimensional van der Waals ferromagnetic semiconductor CrSiTe 3 has attracted growing interest as an intrinsic topological magnet. Both superconductivity and enhancement of ferromagnetism, usually competing for orders, have been observed in CrSiTe 3 at high pressure. However, the high-pressure structure of CrSiTe 3 is still unclear, setting obstacles in understanding pressure-induced novel physics. Here, combining the Raman spectra and first-principles calculations, the structure of CrSiTe 3 at high pressure has been clarified. The interlayer breathing mode located at ∼42.1 cm -1 has been observed for the first time in CrSiTe 3 by ultralow-frequency Raman spectroscopy at high pressure. Theoretical calculations confirm a phase transition from the R 3̅ phase to the R 3 phase accompanying noticeable enhancement of the Curie temperature. Our results highlight ultralow-frequency Raman spectroscopy combined with high pressure for detecting and modulating the structure and interlayer coupling of two-dimensional materials.