Quantum phase transitions in low dimensional superconductors

In low dimensional superconductors fluctuations are enhanced and can dramatically change the properties of the system.  Motivated by experimental observation of superconductor to insulator transitions in wires and thin films we study how the proliferation of topological excitations (quantum phase slips, and quantum vortices) facilitate the transition. In disordered films a parallel magnetic filed can drive such a transition by reducing the superconducting stiffness and thus allowing easier proliferation of quantum vortices. Our quantitative theory allows to distinguish between spin and orbital mechanisms. In addition, our study shows that in order to understand the experimentally observed sharp transition short wires it is necessary to invoke interactions between quantum phase slips, which we treat in a self consistent manner.