Electronic structure of layered1T−TaSe2in commensurate charge-density-wave phase studied by angle-resolved photoemission spectroscopy

Abstract

We present a detailed angle-resolved photoemission study of the electronic structure of layered $1T\ensuremath{-}{\mathrm{TaSe}}_{2}$ in the commensurate charge-density-wave (CDW) phase. A considerable reduction in the spectral weight of a quasiparticle band centered at the binding energy of about 0.25 eV below the Fermi level is observed in the momentum space ranging from the end of the first surface Brillouin zone to the second surface Brillouin zone. Moreover, no crossings of the Fermi level are visible in the whole Brillouin zone, meaning that the Fermi level lies in a pseudogap created by the tails of two overlapping Hubbard subbands. Our results indicate that not only the electron-phonon coupling, which is responsible for the formation of the CDW, but also the subsequent electron correlation effects in the Ta $5d$ band play an important role for the establishment of electronic structure of $1T\ensuremath{-}{\mathrm{TaSe}}_{2}$ in the commensurate CDW phase.