Quantum Criticality in Resonant Andreev Conduction

Motivated by recent experiments with proximitized nanowires, we study a mesoscopic $s$-wave superconductor connected via point contacts to normal-state leads. We demonstrate that at energies below the charging energy the system is described by the two-channel Kondo model, which can be brought to the quantum critical regime by varying the gate potential and conductances of the contacts.

Figure 1

Left panel: Nonmonotonic temperature dependence of the conductance at the Coulomb-blockade peak for asymmetric contacts with $g_L=0.2$ and $g_R=0.3$, corresponding to $T_K^L/T_K^R\sim {10}^{-8}$. Right panel: Temperature dependence of the conductance in the universal regime $T\sim T_F\ll T_K$, see Eq. (18).