  A magnetic impurity coupled to a superconductor gives rise to a
Yu-Shiba-Rusinov (YSR) state inside the superconducting energy gap. With
increasing exchange coupling the excitation energy of this state eventually
crosses zero and the system switches to a YSR groundstate with bound
quasiparticles screening the impurity spin by $\hbar/2$. Here we explore InAs
nanowire double quantum dots tunnel coupled to a superconductor and demonstrate
YSR screening of spin-1/2 and spin-1 states. Gating the double dot through 9
different charge states, we show that the honeycomb pattern of zero-bias
conductance peaks, archetypal of double dots coupled to normal leads, is
replaced by lines of zero-energy YSR states. These enclose regions of
YSR-screened dot spins displaying distinctive spectral features, and their
characteristic shape and topology change markedly with tunnel coupling
strengths. We find excellent agreement with a simple zero-bandwidth
approximation, and with numerical renormalization group calculations for the
two-orbital Anderson model.
