Parity-dependent shot noise and spin-flip relaxation process in a hybrid superconductor-nanowire quantum dot

TL;DR

This study investigates shot noise behavior in a superconductor-nanowire quantum dot, revealing parity-dependent noise characteristics linked to spin-flip relaxation, with results aligning with theoretical models of cotunneling.

Contribution

It provides the first experimental observation of parity-dependent shot noise in a superconductor-nanowire quantum dot, incorporating spin-flip relaxation effects into the theoretical framework.

Findings

Super-Poissonian shot noise with Fano factor ~2 for even parity

Poissonian shot noise with Fano factor ~1 for odd parity

Parity effect disappears under increasing magnetic field

Abstract

We report shot noise measurements for a quantum dot formed in an InAs nanowire suspended between superconducting electrodes. We find a clear alternation for the shot noise value in the Coulomb blockade regime between even and odd electron occupation in the dot, indicating that super-Poissonian (Poissonian) shot noise with the Fano factor reaching around 2 (1) occurs for even (odd) parity. With increasing magnetic field, the parity effect disappears and all the regimes show the Fano factor of around 1. The whole observation in our experiments quantitatively agrees with simulation obtained from full-counting statistics of cotunneling including spin-flip relaxation process, which corresponds to modelling electron motion in a quantum dot with strong spin-orbit interaction.