  Using Indium on Si(111) as an atomically thin superconductor platform, and by
systematically controlling the density of nano-hole defects (nanometer size
voids), we reveal the impacts of defects density and defects geometric
arrangements on superconductivity at macroscopic and microscopic length scales.
When nano-hole defects are uniformly dispersed in the atomic layer, the
superfluid density monotonically decreases as a function of defect density
(from 0.7% to 5% of the surface area) with minor change in the transition
temperature Tc, measured both microscopically and macroscopically. With a
slight increase in the defect density from 5% to 6%, these point defects are
organized into defect chains that enclose individual two-dimensional patches.
This new geometric arrangement of defects dramatically impacts the
superconductivity, leading to the total disappearance of macroscopic superfluid
density and the collapse of the microscopic superconducting gap. This study
sheds new light on the understanding of how local defects and their geometric
arrangement impact superconductivity in the two-dimensional limit.
