Exploring the origin of the thickness-dependent metal-insulator transition in thin-film systems with band structures

Metal-insulator transition (MIT) has been studied in decades and is well known to be induced by temperature, pressure, and dopants. However, the origin of MIT in thin films which occur as metallic thin films become thinner is not explained. In order to investigate the thickness-dependent MIT, transport measurements and photoemission spectroscopy have been performed, however, the conclusion is not to be determined yet. Here, we observed band structures of SrRuO₃ ultrathin films near the MIT-critical thickness by using in-situ angle-resolved photoemission spectroscopy (ARPES). We expect our experimental observation sheds light on the thickness-dependent MIT in thin-film systems.