Spin Properties of Heavy Holes in Low-Dimensional Quantum Electronic Devices

The rich spin physics in quantum confined holes has attracted significant ongoing research interest for over 20 years. The ability to manipulate the spin degrees of freedom in spin-orbit coupled holes via an electric field has opened up the field of spin-based electronics, or spintronics. In this thesis, 1D quantum point contact (QPC) devices are used to probe spin physics, and 2D Hall bar devices are used to test new wafer designs and fabrications methods for controlling the spin-orbit interaction. In 1D systems, the anomalous shoulder on the first subband, known as the 0:7 anomaly, has remained an open problem in mesoscopic spin physics for 20 years. More recently, 1D systems have attracted research interest in the search for the ‘spin gap’. Here we use holes QPCs with strong spin-orbit interaction (SOI) to observe both the 0:7 anomaly and an emergent spin gap for the first time. Recent theory allows us to examine the roles of exchange interactions and SOI on the 0:7 anomaly and spin gap and propose a set of design criteria for devices to show observable spin gap. We then turn to investigating the spin physics in the higher 1D subbands. We demonstrate the dependence of the anisotropy of the in-plane 1D hole g-factor on GaAs cubic crystal anisotropies, and are able to probe the structure of the SOI to extract new information about previously unknown terms in the Hamiltonian for 1D holes. We also present preliminary Zeeman spin-splitting measurements of 1D holes on (111)B GaAs, where persistent spin helix states are predicted to occur. Finally, we describe new techniques for controlling and probing the spin-orbit interaction. Complete characterisation and understanding of the 0:7 anomaly and spin gap, and the interplay between Dresselhaus and Rashba SOI could be achieved in a device with completely tunable symmetry of the quantum confinement. While fabrication methods exist that allow for tunable Rashba SOI, they are expensive and difficult to reproduce. Here we present a new method of device fabrication on GaAs wafer with an in-situ p-type back-gate and show that we can tune the Rashba SOI while maintaining fixed hole density.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2018

Author dc:creator

• Hudson, Karina

• Semiconductor
• GaAs
• Low temperature
• Quantum point contact
• Spin

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/3641

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/61524