Tunable spin/charge Kondo effect at a double superconducting island connected to two spinless quantum wires

Abstract

We propose that a pertinently engineered double superconducting island connected to two spinless one-dimensional conducting leads can work as a tunable spin/charge-Kondo sytem. We evidence how, by tuning a single gate voltage applied to the island, it is possible to make the system switch from the spin-, to the charge-Kondo phase, passing across an intermediate phase, in which the Kondo impurity is effectively irrelevant for the low-temperature behavior of the system. Eventually, we evidence how to probe the various phases by measuring the dependence on the temperature of the dc conductance tensor of our system, by emphasizing the features that should allow to identify the onset of the so far quite elusive charge-Kondo effect.