Quantum charge fluctuations of a proximitized nanowire

Article

关键词: BIAS CONDUCTANCE PEAK;    COULOMB-BLOCKADE;    TOPOLOGICAL SUPERCONDUCTOR;    SEMICONDUCTOR NANOWIRE;    MAJORANA FERMIONS;    SCALING THEORY;    HYBRID DEVICE;    COHERENCE;   

DOI  :  10.1103/PhysRevB.94.125407

来源: SCIE

【 摘 要 】

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 Q of the nanowire is controlled by gate voltage eN(g)/C. A finite conductance of the contact allows for quantum charge fluctuations, making the function Q(N-g) continuous. It depends on the relation between the superconducting gap Delta and the effective charging energy E-C*. The latter is determined by the junction conductance in addition to the geometrical capacitance of the proximitized nanowire. We investigate Q(N-g) at zero magnetic field B and at fields exceeding the critical value B-c corresponding to the topological phase transition [Phys. Rev. Lett. 105, 077001 (2010); 105, 177002 (2010)]. Unlike the case of Delta = 0, the function Q(N-g) is analytic even in the limit of negligible level spacing in the nanowire. At B = 0 and Delta > E-C*, the maxima of dQ/dN(g) are smeared by 2e fluctuations described by a single-channel charge Kondo physics, whereas the B = 0, Delta < E-C* case is described by a crossover between the Kondo and the mixed-valence regimes of the Anderson impurity model. In the topological phase, Q(N-g) is an analytic function of the gate voltage with e-periodic steps. In the weak-tunneling limit, dQ/dN(g) has peaks corresponding to Breit-Wigner resonances, whereas in the strong-tunneling limit (i.e., small reflection amplitude r) these resonances are broadened, and dQ/dN(g) - e alpha r cos(2 pi N-g).

【 授权许可】

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