Supergap anomalies in cotunneling between N-S and between S-S leads via a small quantum dot

Abstract

Cotunneling current through a resonant level coupled to either normal and superconducting or to two superconducting leads is studied for the domain of bias voltages, V, exceeding the superconducting gap, 2Δ. Due to the on-site repulsion in the resonant level, cotunneling of an electron is accompanied by creation of a quasiparticle in a superconducting lead. Energy conservation imposes a threshold for this inelastic transport channel: V_c=3Δfor N-S case and \tilde{V}_c=4Δfor the S-S case. We demonstrate that the behavior of current near the respective thresholds is nonanalytic, namely, δI^{in}(V)\propto (V-V_c)^{3/2}Θ(V-V_c) and δI^{in}(V) \propto (V-\tilde{V}_c)Θ(V-\tilde{V}_c). Stronger anomaly for the S-S leads is the consequence of the enhanced density of states at the edges of the gap. In addition, the enhanced density of states makes the threshold anomalies for two-electron cotunneling processes in the Coulomb-blockaded regions more pronounced than for the N-N leads.

11 pages, 7 figures

References in corpus (8)

• Quantum supercurrent transistors in carbon nanotubes
• Inelastic electron tunneling via molecular vibrations in single-molecule transistors
• Josephson current through a single Anderson impurity coupled to BCS leads
• Even-odd effect in Andreev Transport through a Carbon Nanotube Quantum Dot
• Kondo-Enhanced Andreev Tunneling in InAs Nanowire Quantum Dots
• Kondo Universal Scaling for a Quantum Dot Coupled to Superconducting Leads
• Lateral electron tunneling through single self-assembled InAs quantum dots coupled to superconducting nanogap electrodes
• Electron Pair Resonance in the Coulomb Blockade

Cited by in corpus (2)

• Andreev reflection versus Coulomb blockade in hybrid semiconductor nanowire devices
• Polaron effects on the dc- and ac-tunneling characteristics of molecular Josephson junctions