thin films studied by high-resolution ARPES*

Atomically-thin transition metal dichalcogenides are a target of intensive studies since they show variety of exotic physical properties such as robust charge-density-waves (CDW) and two-dimensional superconductivity. We have fabricated monolayer and multilayer VTe₂ thin films on bilayer graphene by molecular-beam-epitaxy method and studied their electronic states by angle-resolved photoemission spectroscopy. We clearly found a drastic difference in the Fermi-surface topology between monolayer and multilayer VTe₂ films, suggesting an occurrence of structural phase transition from regular octahedral (1T) to distorted octahedral (1T') phase. We discuss the origin of structural phase transition in terms of the CDW and Jahn-Teller effect.