Parity effect in superconducting aluminum single electron transistors with spatial gap profile controlled by film thickness

TL;DR

This paper introduces a new method to suppress quasiparticle poisoning in aluminum single electron transistors by controlling the energy gap profile through film thickness, leading to improved device performance.

Contribution

The study demonstrates that adjusting film thickness to create a spatial gap profile effectively suppresses quasiparticle poisoning in superconducting devices.

Findings

Suppression of quasiparticle poisoning confirmed by transport measurements

Observation of clear 2e periodicity when island is thinner than leads

Validation of the gap profile control method as effective

Abstract

We propose a novel method for suppression of quasiparticle poisoning in Al Coulomb blockade devices. The method is based on creation of a proper energy gap profile along the device. In contrast to the previously used techniques, the energy gap is controlled by the film thickness. Our transport measurements confirm that the quasiparticle poisoning is suppressed and clear 2$e$ periodicity is observed only when the island is made much thinner than the leads. This result is consistent with the existing model and provides a simple method to suppress quasiparticle poisoning.