Lecturer: Karl Berggren (MIT)

Abstract: Superconductors are broadly familiar as detectors of magnetic field. But their use as single-photon detectors, and now as components of electronics circuits, has begun to emerge. These potential applications have led us to study the fascinating physical properties of these materials: an enormous intrinsic nonlinear response, and extraordinarily low carrier density. As a consequence, thin films of superconductors like niobium nitride exhibit enormous kinetic inductance at low frequencies, a property unique to highly plasmonic materials. Their effective "magnetic" (not actually due to magnetic field) permeability is thus 100s of times the permeability of free space. The direct consequence is a speed of signal propagation of a few percent of the speed of light, and characteristic impedances in the kΩ range. These extreme properties makes these systems ideal for a range of applications in single-photon detection, digital and analog electronics, and even dark-matter detection. As an engineering platform, this system thus presents fascinating opportunities for future work, while as a physical system, it continue to offer exciting new phenomena for study.