Photoemission study of valence band dispersions in charge density wave material 1T-TaS 2

Abstract

Angle-resolved photoemission spectra of 1T-TaS 2 have been measured to reveal the electronic structure of valence bands in the incommensurate (IC) and commensurate (C) charge density wave (CDW) phases. In the ICCDW phase at 370 K, Ta 5d states are observed as a single branch along the Γ–M direction over the binding energy range E B=0–1.2 eV. In the CCDW phase at 17 K, on the other hand, Ta 5d states are divided into three sub-band manifolds centered at E B=0.2, 0.5 and 1.0 eV. The former sub-band at E B=0.2 eV is less dispersive, while latter two show clear dispersive nature with the bandwidths of ∼0.5 and 0.3 eV. Furthermore, the spectral intensities are concentrated around the original Ta 5d band.