Enhanced Andreev Tunneling via the Kondo Resonance in a Quantum Dot at Finite Bias

Abstract

We study the nonequilibrium transport through a quantum dot coupled to normal and superconducting leads. We use the modified second-order perturbation theory to calculate the differential conductance and the local density of states at the quantum dot. In the strong but finite Coulomb interaction regime, the differential conductance shows an anomalous peak not at a zero bias voltage but at a finite bias voltage. We also observe an additional Kondo resonance besides the normal one in the local density of states, where the former is caused by nonequilibrium Andreev tunneling via the normal Kondo resonance. We explain that this specific Andreev tunneling gives rise to the anomalous peak in the differential conductance. Since the Andreev tunneling via the Kondo resonance is suppressed with increasing temperature, the anomalous peak in the differential conductance disappears at high temperatures.

arXiv comment4 pages, 4 figures

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• Renormalization effects in interacting quantum dots coupled to superconducting leads
• Finite-frequency noise in a quantum dot with normal and superconducting leads
• Many-body perturbation theory for the superconducting quantum dot: Fundamental role of the magnetic field
• Failure of the mean-field description of magnetic fluctuations in the superconducting quantum dot
• Properties of multiterminal superconducting nanostructure with double quantum dot