The Shiba molecule

We analyze the phase diagram associated with a pair of magnetic impurities trapped in a superconducting host The natural interplay between Kondo screening superconductivity and exchange interactions leads to a rich array of competing phases whose transitions are characterized by discontinuous changes of the total spin Our analysis is based on a combination of numerical renormalization group techniques as well as semi classical analytics In addition to the expected screened and unscreened phases we observe a new molecular doublet