  Superconductivity is among the most fascinating and well-studied quantum
states of matter. Despite over 100 years of research, a detailed understanding
of how features of the normal-state electronic structure determine
superconducting properties has remained elusive. For instance, the ability to
deterministically enhance the superconducting transition temperature by design,
rather than by serendipity, has been a long sought-after goal in condensed
matter physics and materials science, but achieving this objective may require
new tools, techniques and approaches. Here, we report the first instance of the
transmutation of a normal metal into a superconductor through the application
of epitaxial strain. We demonstrate that synthesizing RuO$_{2}$ thin films on
(110)-oriented TiO$_{2}$ substrates enhances the density of states near the
Fermi level, which stabilizes superconductivity under strain, and suggests that
a promising strategy to create new transition-metal superconductors is to apply
judiciously chosen anisotropic strains that redistribute carriers within the
low-energy manifold of $d$ orbitals.
