Superconductivity of very thin films: The superconductor–insulator transition

• This manuscript reviews work on the superconductor–insulator transitions of investigated in metallic film, cuprates and metallic interfaces.
• Superconductor–insulator transitions are examples of quantum phase transitions.
• The systems discussed serve as model systems for behaviors found in more complex systems of contemporary interest.
• The concept of a quantum phase transition is an important paradigm in condensed matter physics.
• The review also includes discussions of open issues.

The study of thin superconducting films has been an important component of the science of superconductivity for more than six decades. It played a major role in the development of currently accepted views of the macroscopic and microscopic nature of the superconducting state. In recent years the focus of research in the field has shifted to the study of ultrathin films and surface and interface layers. This has permitted the exploration of one of the important topics of condensed matter physics, the superconductor–insulator transition. This review will discuss this phenomenon as realized in the study of metallic films, cuprates, and metallic interfaces. These are in effect model systems for behaviors that may be found in more complex systems of contemporary interest.