Anisotropic Pauli spin blockade in hole quantum dots

TL;DR

This paper investigates anisotropic Pauli spin blockade phenomena in hole quantum dots within Ge-Si nanowires, revealing spin-flip mechanisms and guiding optimal magnetic field orientations for spin qubit stability.

Contribution

It demonstrates the observation of anisotropic spin-flip cotunneling and spin-orbit coupling effects in hole quantum dots, providing insights for enhancing spin qubit coherence.

Findings

Observation of Pauli spin blockade in Ge-Si nanowire quantum dots

Identification of anisotropic spin-flip cotunneling mechanisms

Signatures of spin-orbit coupling affecting leakage current

Abstract

We present measurements on gate-defined double quantum dots in Ge-Si core-shell nanowires, which we tune to a regime with visible shell filling in both dots. We observe a Pauli spin blockade and can assign the measured leakage current at low magnetic fields to spin-flip cotunneling, for which we measure a strong anisotropy related to an anisotropic g-factor. At higher magnetic fields we see signatures for leakage current caused by spin-orbit coupling between (1,1)-singlet and (2,0)-triplet states. Taking into account these anisotropic spin-flip mechanisms, we can choose the magnetic field direction with the longest spin lifetime for improved spin-orbit qubits.