Abstract
Motivated by a recent experiment [Nature (London) 531, 206 (2016)], we consider charging of a nanowire which is proximitized by a superconductor and connected to a normal-state lead by a single-channel junction. The charge of the nanowire is controlled by gate voltage . A finite conductance of the contact allows for quantum charge fluctuations, making the function continuous. It depends on the relation between the superconducting gap and the effective charging energy . The latter is determined by the junction conductance in addition to the geometrical capacitance of the proximitized nanowire. We investigate at zero magnetic field and at fields exceeding the critical value corresponding to the topological phase transition [Phys. Rev. Lett. 105, 077001 (2010); Phys. Rev. Lett. 105, 177002 (2010)]. Unlike the case of , the function is analytic even in the limit of negligible level spacing in the nanowire. At and , the maxima of are smeared by fluctuations described by a single-channel “charge Kondo” physics, whereas the case is described by a crossover between the Kondo and the mixed-valence regimes of the Anderson impurity model. In the topological phase, is an analytic function of the gate voltage with -periodic steps. In the weak-tunneling limit, has peaks corresponding to Breit-Wigner resonances, whereas in the strong-tunneling limit (i.e., small reflection amplitude ) these resonances are broadened, and .
- Received 5 July 2016
DOI:https://doi.org/10.1103/PhysRevB.94.125407
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