  Superconductivity results from a Bose condensate of Cooper-paired electrons
with a macroscopic quantum wavefunction. Dramatic effects can occur when the
region of the condensate is shaped and confined to the nanometer scale. Recent
progress in nanostructured superconductors has revealed a route to topological
superconductivity, with possible applications in quantum computing. However,
challenges remain in controlling the shape and size of specific superconducting
materials. Here, we report a new method to create nanostructured
superconductors by partial crystallization of the half-Heusler material, YPtBi.
Superconducting islands, with diameters in the range of 100 nm, were
reproducibly created by local current annealing of disordered YPtBi in the
tunneling junction of a scanning tunneling microscope (STM). We characterize
the superconducting island properties by scanning tunneling spectroscopic
measurements to determine the gap energy, critical temperature and field,
coherence length, and vortex formations. These results show unique properties
of a confined superconductor and demonstrate that this new method holds promise
to create tailored superconductors for a wide variety of nanometer scale
applications.
