Dimensional-Crossover-Driven Metal-Insulator Transition in SrVO3 Ultrathin Films

We have investigated the changes occurring in the electronic structure of digitally controlled SrVO3 ultrathin films across the metal-insulator transition (MIT) by the film thickness using in situ photoemission spectroscopy. With decreasing film thickness, a pseudogap is formed at EF through spectral weight transfer from the coherent part to the incoherent part. The pseudogap finally evolves into an energy gap that is indicative of the MIT in a SrVO3 ultrathin film. The observed spectral behavior is reproduced by layer dynamical-mean-field-theory calculations, and it indicates that the observed MIT is caused by the reduction in the bandwidth due to the dimensional crossover.