Condensed Matter Seminars

Superconductivity in two dimensions provides a unique area in which a fascinating variety of novel and fundamental phenomena occur. In this talk, I will review recent theoretical and experimental results on disordered films, which undergo a magnetic field tuned superconducting-insulator transition at low temperatures. I will focus on the unusual phases and fluctuation phenomena evident in the experimental studies of the field-tuned transition. First, I will explain how rare disorder fluctuations can enhance global superconductivity and increase the critical magnetic field at which samples become superconducting. Next, I will briefly summarize the recently developed theory of quantum superconducting fluctuations, which explains transport properties above the transition. At the end of my talk, I will focus on the low-temperature metallic phase observed in certain materials. This metallic state is truly mysterious and can not be explained by any conventional theory (involving bosonic vortices as basic excitations). I will argue that under certain circumstances the statistics of the vortices can change from bosonic to fermionic. Such a statistical transmutation may explain the nature of the metallic state. I will discuss possible experimental signatures of the resulting vortex Fermi liquid.