Multiple Andreev reflection in single-atom niobium junctions

B. Ludoph; N. van der Post; E. N. Bratus’; E. V. Bezuglyi; V. S. Shumeiko; G. Wendin; J. M. van Ruitenbeek

doi:10.1103/PhysRevB.61.8561

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Multiple Andreev reflection in single-atom niobium junctions

B. Ludoph, N. van der Post, E. N. Bratus’, E. V. Bezuglyi, V. S. Shumeiko, G. Wendin, J. M. van Ruitenbeek

DOI 10.1103/PhysRevB.61.8561 · Physical Review B

T1

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Abstract

Single-atom junctions between superconducting niobium leads are produced using the mechanically controllable break junction technique. The current-voltage characteristics of these junctions are analyzed using an exact formulation for a superconducting quantum point contact. For tunneling between two single atoms with a sufficiently large vacuum barrier, it is found that a single channel dominates the current, and that the current-voltage characteristic is described by the theory, without adjustable parameters. For a contact of a single Nb atom it is shown that five conductance channels contribute to the conductance, in agreement with the number expected based on the number of valence orbitals for this d metal. For each of the channels the transmission probability is obtained from the fits, and the limits of accuracy of these numbers are discussed.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown