Pressure-induced superconductivity and nontrivial band topology in compressed gamma-InSe

We performed high-pressure electrical transport and Raman measurements on a two-dimensional rhombohedral semiconductor gamma-InSe. Our results confirm two structural phase transitions at high pressure. More interestingly, a domelike superconducting transition with maximum T-c around 2.3 K is discovered when the compound transforms to the cubic CsCl phase above 40 GPa. Our first-principles calculations indicate that the high-pressure superconducting phase possesses nontrivial topological band structure in the vicinity of the Fermi level. These results show that the physical properties in this material strongly depend on its structure, which provides insights into the interplay between superconductivity and topological physics. Our work suggests promising emergent phenomena in this material and other related III-VI semiconductors under high-pressure conditions.