Periodicity in Al/Ti superconducting single electron transistors

TL;DR

This study demonstrates that engineering the superconducting gap profile in Ti/Al single-electron transistors can suppress quasiparticle poisoning, leading to more stable 2e periodicity in transport measurements.

Contribution

The paper introduces a novel approach of using different superconducting materials to control quasiparticle poisoning in single-electron transistors.

Findings

TiAlTi devices show suppressed quasiparticle poisoning with 2e periodicity.

AlTiAl devices exhibit full quasiparticle poisoning with e periodicity.

Gap profile engineering affects the electronic transport behavior.

Abstract

We present experiments on single Cooper-pair transistors made of two different superconducting materials. We chose Ti and Al to create an energy gap profile such that the island has a higher gap than the leads, thereby acting as a barrier to quasiparticle tunneling. Our transport measurements demonstrate that quasiparticle poisoning is suppressed in all our TiAlTi structures (higher gap for the island) with clear 2e periodicity observed, whereas full quasiparticle poisoning is observed in all AlTiAl devices (higher gap for the leads) with e periodicity.