Quasi One-Dimensional Band Structure of Photoinduced Semimetal Phase of Ta2Ni1-xCoxSe5 (x=0.0 and 0.1)

The photoinduced semimetal phase of Ta2Ni1-xCoxSe5 (x = 0.0 and 0.1) is studied by time-resolved angle-resolved photoemission spectroscopy. The observed band dispersions roughly agree with the generalized gradient approximation (GGA) calculation which fails to reproduce the band gap at the ambient condition. This suggests that the electron-hole interaction, which is not exactly included in GGA, is screened out by the photoexcited carriers. There is no indication of pseudogap. The conduction and valence bands provide quasi one-dimensional Fermi surfaces with similar momentum positions suggesting a quasi one-dimensional line-node semimetal.