We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) of layered chalcogenide 1$T$-TaS${}_{2-x}$Se${}_x$ to elucidate the electronic states especially relevant to the occurrence of superconductivity. We found a direct evidence for a Ta-5$d$-derived electron pocket associated with the superconductivity, which is fragile against a Mott-gap opening observed in the insulating ground state for S-rich samples. In particular, a strong electron-electron interaction-induced Mott gap driven by a Ta 5$d$ orbital also exists in the metallic ground state for Se-rich samples, while finite ARPES intensity near the Fermi level likely originating from a Se 4$p$ orbital survives, indicative of the orbital-selective nature of the Mott transition. Present results suggest that effective electron correlation and $p$-$d$ hybridization play a crucial role to tune the superconductivity and Mott metal-insulator transition.

• Received 1 August 2013

DOI:https://doi.org/10.1103/PhysRevB.88.115145