The rich phenomena in the FeSe and related compounds have attracted great interests as it provides fertile material to gain further insight into the mechanism of high temperature superconductivity. A natural follow-up work was to look into the possibility of superconductivity in MnSe. It was shown that MnP becomes superconducting with Tc ~ 1 K under pressure. We demonstrated in this work that high pressure can effectively suppress the complex magnetic characters of MnSe crystal when observed at ambient condition. MnSe under pressure is found to undergo several structural transformations: the cubic phase first partially transforms to the hexagonal phase at about 12 GPa, the crystal exhibits the coexistence of cubic, hexagonal and orthorhombic phases from 16 GPa to 30 GPa, and above 30 GPa the crystal shows a single orthorhombic phase. Superconductivity with Tc ~ 5 K was first observed at pressure ~12 GPa by magnetic measurements (~16 GPa by resistive measurements). The highest Tc is ~ 9 K (magnetic result) at ~35 GPa. Our observations suggest the observed superconductivity may closely relate to the pressure-induced structural change. However, the interface between the metallic and insulating boundaries may also play an important role to the pressure induced superconductivity in MnSe.
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