Magnetic Field Evolution of Spin Blockade in Ge/Si Nanowire Double Quantum Dots

TL;DR

This study investigates the magnetic field effects on spin blockade in Ge/Si nanowire double quantum dots, revealing complex leakage current behavior and quantifying spin-orbit interaction and g-factors.

Contribution

It provides new insights into spin blockade phenomena in Ge/Si nanowires, including measurements of spin-orbit length and anisotropic g-factors, advancing understanding of spin dynamics in these systems.

Findings

Leakage current shows both dip and peak at zero magnetic field.

Lower bound for spin-orbit length is 500 nm.

Large, anisotropic g-factors are observed, larger than previous reports.

Abstract

We perform transport measurements on double quantum dots defined in Ge/Si core/shell nanowires and focus on Pauli spin blockade in the regime where tens of holes occupy each dot. We identify spin blockade through the magnetic field dependence of leakage current. We find both a dip and a peak in the leakage current at zero field. We analyze this behavior in terms of the quantum dot parameters such as coupling to the leads, interdot tunnel coupling as well as spin-orbit interaction. We find a lower bound for spin-orbit interaction with $l_{\rm so}=500$ nm. We also extract large and anisotropic effective Land$\rm \acute{e}$ g-factors, with larger g-factors in the direction perpendicular to the nanowire axis in agreement with previous studies and experiments but with larger values reported here.