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

The electronic structure of digitally controlled SrVO₃ ultrathin films was investigated using in situ photoemission spectroscopy. We observed a pseudogap formed at E_F with decreasing the film thickness accompanying the spectral weight transfer from the low-energy coherent part to the high-energy incoherent part. The pseudogap finally evolves into an energy gap in a SrVO₃ ultrathin film indicating the metal-insulator transition. The layer dynamical-mean-field-theory calculation suggests that the observed metal-insulator transition is caused by the reduction in the bandwidth due to the dimensional crossover. Right figures show the comparison between the experimental results (left panel) and theoretical ones (right panel). This work was done by K. Yoshimatsu, T. Okabe, H. Kumigashira, S. Aizaki, A. Fujimori, M. Oshima at the University of Tokyo, and S. Okamoto. Phys. Rev. Lett. 104, 147601 (2010)