Emergence of high-temperature superconductivity in a Ca₂RuO₄ nanocrystals

The search for high-temperature (high-T_c) superconductors is a fascinating topic in condensed matter physics. It is widely believed that high-T_c superconductivity in cuprates emerges from doped Mott insulators. Recently, 4d and 5d transition metal oxides with a layer perovskite structure have attracted much attention because the possibility of the emergence of high-T_c superconductivity has been recognized in several studies.
Here we report the realization of high-temperature superconductivity in Ca₂RuO₄ nanofilm single crystals. We found that the induced bias current and the tuned film thickness cause a superconductor-insulator transition. We clarify two quantum critical phase transitions corresponding to the clean and dirty limits of the Harris criterion. Our results demonstrate the presence of two-dimensional high-temperature superconductivity in Ca₂RuO₄ nanofilm.