  Layered transition-metal dichalcogenides 1T-TaS2-xSex (0<=x<=2) single
crystals have been successfully fabricated by using a chemical vapor transport
technique in which Ta locates in octahedral coordination with S and Se atoms.
This is the first superconducting example by the substitution of S site, which
violates an initial rule based on the fact that superconductivity merely
emerges in 1T-TaS2 by applying the high pressure or substitution of Ta site. We
demonstrate the appearance of a series of electronic states in 1T-TaS2-xSex
with Se content. Namely, the Mott phase melts into a nearly commensurate
charge-density-wave (NCCDW) phase, superconductivity in a wide x range develops
within the NCCDW state, and finally commensurate charge-density-wave (CCDW)
phase reproduces for heavy Se content. The present results reveal that
superconductivity is only characterized by robust Ta 5d band, demonstrating the
universal nature in 1T-TaS2 systems that superconductivity and NCCDW phase
coexist in the real space.
