Even-odd effect in Andreev Transport through a Carbon Nanotube Quantum Dot

Abstract

We have measured the current(I)-voltage(V) characteristics of a single-wall carbon nanotube quantum dot coupled to superconducting source and drain contacts in the intermediate coupling regime. Whereas the enhanced differential conductance dI/dV due to the Kondo resonance is observed in the normal state, this feature around zero bias voltage is absent in the superconducting state. Nonetheless, a pronounced even-odd effect appears at finite bias in the $dI/dV$ sub-gap structure caused by Andreev reflection. The first-order Andreev peak appearing around V=Δ/e is markedly enhanced in gate-voltage regions, in which the charge state of the quantum dot is odd. This enhancement is explained by a `hidden' Kondo resonance, pinned to one contact only. A comparison with a single-impurity Anderson model, which is solved numerically in a slave-boson meanfield ansatz, yields good agreement with the experiment.

References in corpus (7)

• Tunable Supercurrent Through Semiconductor Nanowires
• Supercurrent reversal in quantum dots
• Quantum supercurrent transistors in carbon nanotubes
• Kondo effect in quantum dots
• Kondo-Enhanced Andreev Tunneling in InAs Nanowire Quantum Dots
• Transport spectroscopy of Kondo quantum dots coupled by RKKY interaction
• Interplay between Josephson effect and magnetic interactions in double quantum dots

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• Andreev Transport through Side-Coupled Double Quantum Dots
• Meservey-Tedrow-Fulde effect in a quantum dot embedded between metallic and superconducting electrodes
• Superconducting non-equilibrium transport through a weakly interacting quantum dot
• Supercurrent and multiple singlet-doublet phase transitions of a quantum dot Josephson junction inside an Aharonov-Bohm ring
• Gate Tunable Dissipation and "Superconductor-Insulator" Transition in Carbon Nanotube Josephson Transistors
• Critical and excess current through an open quantum dot: Temperature and magnetic field dependence
• Supergap anomalies in cotunneling between N-S and between S-S leads via a small quantum dot