Elementary Andreev Processes in a Driven Superconductor-Normal Metal Contact

TL;DR

This paper analyzes the full counting statistics of a voltage-driven N-S contact, revealing elementary Andreev processes and optimal quantization conditions for Lorentzian voltage pulses, especially half-integer Levitons.

Contribution

It provides a detailed theoretical analysis of Andreev processes in a driven superconductor-normal metal contact, including the effects of Lorentzian voltage pulses.

Findings

Elementary processes include single and electron/hole-like Andreev transfers.

Transport characteristics can be derived from normal metal results with appropriate substitutions.

Half-integer Levitons achieve optimal quantization in this setup.

Abstract

We investigate the full counting statistics of a voltage-driven normal metal(N)-superconductor(S) contact. In the low-bias regime below the superconducting gap, the NS contact can be mapped onto a purely normal contact, albeit with doubled voltage and counting fields. Hence in this regime the transport characteristics can be obtained by the corresponding substitution of the normal metal results. The elementary processes are single Andreev transfers and electron- and hole-like Andreev transfers. Considering Lorentzian voltage pulses we find an optimal quantization for half-integer Levitons.