Electronic structure reconstruction for 3 × 3 charge density wave in heavily Cu-intercalated TiSe 2 revealed by spatially resolved photoemission spectroscopy

Scanning photoemission microscopy (SPEM) and angle-resolved photoemission spectroscopy (ARPES) are used to investigate the electronic structure of Cu 0.33 TiSe 2 across the charge density wave (CDW) transition. The electronic structure is found to be largely homogeneous in the normal state above the CDW transition. The ARPES measurements using a submicron beam size reveal a large electronlike pocket due to the Ti band at the M point while the Se 4 p band at the Γ point is absent due to electron doping by the intercalated Cu. We have observed 3 × 3 Fermi surface reconstruction below the CDW transition, in which Ti 3 d bands are folded into a reconstructed BZ rotated by 30 ∘ , making the Γ and K points equivalent. The results demonstrate the presence of a 3 × 3 CDW phase in the electronic structure of heavily Cu-intercalated Cu 0.33 TiSe 2 . The findings reveal a platform for investigating the two-dimensional electronic phase in 1T- TiSe 2 chalcogenides, which exhibit a unique interplay between CDW, superconductivity, and excitonic/lattice instabilities.