Critical States in Confined Superconductors: From Mesoscopic Phenomena to Microscopic Understanding – SUPERSTRIPES

The present project addresses fundamental issues in condensed matter physics related to the study of the microscopic parameters affecting the global and local quantum phase coherence of disordered low-dimensional superconductors.

In ultrathin superconductors, the quantum condensate suffers from the effects of disorder and electron correlations which both tend to destroy superconductivity and drive the material to an insulating state [C. Brun et al. Nature Phys. 10, 6, 444-450 (2014)]. Close to this Superconductor-Insulator transition (SIT), electronic inhomogeneities emerge, involving several characteristic nanometer-scale lengths [Y. Noat et al. Phys. Rev. B, 88, 1,014503 (2013)]. By tuning the well-characterized disorder in ultrathin superconducting films, the goal of the proposal is to reveal how the emergent electronic inhomogeneities affect the quantum coherence of the superconducting condensate. The most striking signature of the phase coherence in a superconductor being its ability to sustain a dissipation-less electric current. We will use this superconducting current for approaching the transition to the insulating phase. To probe the phase coherence directly on the local scale, a super-current will be injected in superconducting nanowires, patterned out of a disordered superconducting thin film, while simultaneously probing its local density of states (LDOS) by scanning tunneling microscopy and global electronic properties by transport measurements.