Scientific Calendar Event



Starts 23 Nov 2021 11:00
Ends 23 Nov 2021 12:00
Central European Time
Hybrid seminar: Virtual, and
SISSA 128
via Bonomea, 265 Trieste
Abstract:

The Kondo effect is an archetype of quantum many-body physics: a magnetic impurity coupled antiferromagnetically to a metallic bath results in a strongly correlated ground state in which the bath screens the impurity spin. If the bath is superconducting rather than metallic, a so-called Yu-Shiba-Rusinov (YSR) bound state forms which screens the impurity and whose energy is below the superconducting gap. These YSR states have recently garnered a lot of interest due to applications in topological quantum computing but are typically only studied for BCS superconductors. In this talk I will describe how this BCS picture changes when a Kondo impurity is coupled to a 1-d charge conserving superconductor. By examining the system in various semiclassical limits through bosonization, combined with exact results from Bethe Ansatz the full phase diagram can be determined. The main result is that the enhanced quantum fluctuations lead to the destruction of YSR states in all but a very narrow region of the phase diagram. Within this region, the YSR state facilitates a first order quantum phase transition between a screened and unscreened impurity. Outside this region a renormalized Kondo effect is found on the screened side whereas on the unscreened side the impurity remains strongly coupled to the bulk in contrast to the metallic case.