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.
@article{arxiv.1608.00111,
title = {Anisotropic Pauli spin blockade in hole quantum dots},
author = {Matthias Brauns and Joost Ridderbos and Ang Li and Erik P. A. M. Bakkers and Wilfred G. van der Wiel and Floris A. Zwanenburg},
journal= {arXiv preprint arXiv:1608.00111},
year = {2016}
}