Electron localization probed by temperature-dependent tunneling spectroscopy in 1T-TaS ₂

In order to present a clear picture of the density of states at both sides of the Fermi level (E _F) in 1T-TaS ₂ near the nearly commensurate to commensurate transition (∼ 187 K) and at low temperatures, we have done a temperature-dependent tunneling spectroscopy study using a scanning tunneling microscope. We observed an abrupt transition from a charge-density-wave induced depletion to an opening of a deep pseudo gap near the E _F of the nearly commensurate to commensurate transition within ∼ 1 K. The measured pseudo gap turned out to be deep enough to form localized states at E _F. In contrast to an inverse photoelectron spectroscopy study, our tunneling results indicate the gap structures of two Hubbard subbands resulting from band splitting of the Ta 5d band due to the electron correlation effect.