Pressure-induced coupled structural-electronic transition in SnS under different hydrostatic environments up to 39.7 GPa.

A series of high-pressure Raman spectroscopy and electrical conductivity experiments have been performed to investigate the vibrational and electrical transport properties of SnS under non-hydrostatic and hydrostatic environments. Upon compression, an coupled structural-electronic transition in SnS occurred at 30.2 GPa under non-hydrostatic conditions, which was evidenced by the splitting of the E mode and the discontinuities in Raman shifts, Raman full width at half maximum (FWHM) and electrical conductivity. However, the coupled structural-electronic transition took place at a higher pressure of 33.4 GPa under hydrostatic conditions, which may be due to the influence of the pressure medium. Furthermore, our first-principles theoretical calculations results revealed that the bandgap energy of SnS decreased slowly with increasing pressure and it closed in the pressure range of 30-40 GPa, which agreed well with our Raman spectroscopy and electrical conductivity results. Upon decompression, the recoverable Raman peaks and electrical conductivity indicated that the coupled structural-electronic transition was reversible, which was further confirmed by our HRTEM observations.