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Nonlocal spectroscopy of Andreev bound states

J. Schindele, A. Baumgartner, R. Maurand, M. Weiss, C. Schönenberger

DOI 10.1103/PhysRevB.89.045422 · Physical Review B

T1

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Abstract

We experimentally investigate Andreev bound states (ABSs) in a carbon nanotube quantum dot (QD) connected to a superconducting Nb lead (S). A weakly coupled normal metal contact acts as a tunnel probe that measures the energy dispersion of the ABSs. Moreover, we study the response of the ABS to nonlocal transport processes, namely, Cooper pair splitting and elastic co-tunnelling, which are enabled by a second QD fabricated on the same nanotube on the opposite side of S. We find an appreciable nonlocal conductance with a rich structure, including a sign reversal at the ground-state transition from the ABS singlet to a degenerate magnetic doublet. We describe our device by a simple rate equation model that captures the key features of our observations and demonstrates that the sign of the nonlocal conductance is a measure for the charge distribution of the ABS, given by the respective Bogoliubov-de Gennes amplitudes u and v.

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FormulaReported Tc (K)Pressure (GPa)Type
Nb

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—Pressure not reportedunknown

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