  Various transition metal trichalcogenides (TMTC) show the charge-density-wave
and superconductivity, which provide an ideal platform to study the correlation
between these two orderings and the mechanism of superconductivity. Currently,
almost all metallic TMTC compounds can show superconductivity either at ambient
pressure or at high pressure. However, most TMTC compounds are semiconductors
and even insulators. Does the superconductivity exist in any non-metal TMTC
compound? In this work, we managed to manipulate the electronic behavior of
highly insulating HfS3 in term of pressure. HfS3 underwent an
insulator-semiconductor transition near 17 GPa with a band gap reduce of ~1 eV.
The optical absorption and Raman measurement provide the consistent results,
suggesting the structural origin of the electronic transition. Upon further
compression, HfS3 becomes a superconductor. The superconducting transition was
initialized as early as 50.6 GPa and the zero-resistance is reached above 91.2
GPa. The superconducting behavior is further confirmed by both the magnetic
field effect and current effect. This work sheds the light that all TMTC may be
superconductors, and opens a new avenue to explore the abundant emergence
phenomena in TMTC material family.
