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Resonant and Inelastic Andreev Tunneling Observed on a Carbon Nanotube Quantum Dot

J. Gramich, A. Baumgartner, C. Schönenberger

DOI 10.1103/PhysRevLett.115.216801 · Physical Review Letters

T1

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Abstract

We report the observation of two fundamental subgap transport processes through a quantum dot (QD) with a superconducting contact. The device consists of a carbon nanotube contacted by a Nb superconducting and a normal metal contact. First, we find a single resonance with position, shape, and amplitude consistent with the theoretically predicted resonant Andreev tunneling (AT) through a single QD level. Second, we observe a series of discrete replicas of resonant AT at a separation of ∼145 μeV, with a gate, bias, and temperature dependence characteristic for boson-assisted, inelastic AT, in which energy is exchanged between a bosonic bath and the electrons. The magnetic field dependence of the replica’s amplitudes and energies suggest that two different bosons couple to the tunnel process.

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FormulaReported Tc (K)Pressure (GPa)Type
Nb

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—Pressure not reportedunknown

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