Strong tunneling and charge quantization in S-I-N Coulomb blockade structures

TL;DR

This paper investigates charge quantization in S-I-N Coulomb blockade structures, revealing that Coulomb staircase steps remain sharp despite high conductance, and demonstrating the transition to smeared steps when superconductivity is suppressed by a magnetic field.

Contribution

It presents a novel analysis of charge quantization in S-I-N structures, showing the persistence of sharp Coulomb steps at high conductance levels unlike in N-I-N systems.

Findings

Coulomb staircase steps remain sharp at conductance > e^2/h in S-I-N structures

Magnetic field destroys superconductivity, leading to smeared Coulomb steps

Transition from sharp to smeared steps observed with magnetic field application

Abstract

We study the charge of a small normal island connected by a tunnel junction to a superconducting lead. Unlike the N-I-N case, the steps of the Coulomb staircase remain sharp even if the conductance of the tunneling barrier exceeds e^2/h. One can observe the transition from sharp steps to the smeared ones by applying magnetic field to destroy the superconductivity.