סמינר בחומר מעובה: Kondo Effect in 1-D interacting superconductors (and in dissipative environments)

The study of a Kondo impurity in a BCS superconductors stretches back several decades. It has been found that the impurity is screened by a local bound state – the Yu-Shiba-Rusinov (YSR) intra-gap states. Here we study a Kondo impurity coupled to a one-dimensional charge conserving spin-singlet superconductor. We find that several regimes emerge since quantum fluctuations are enhanced in low dimensional bringing about new behaviors. We show that the Yu-Shiba-Rusinov (YSR) intra-gap bound-states are destroyed in all but a narrow region of the phase diagram, as opposed to a Kondo impurity in BCS superconductors where the Shiba state occurs over the whole phase. We find that for large enough impurity spin exchange interaction a renormalized Kondo-screened regime is established. In this regime there are no YSR states and a renormalized Kondo scale is generated.  For weak coupling, on the other hand, we find a local moment behavior indicating that in this regime the Kondo RG flow undergoes a limit cycle.

If time permits I will also talk about the dissipation-driven Kondo system  whose phase diagram is very similar to the superconductor-Kondo phase diagram.