2018/07/03 by Chung-Tao Chou, Chou, Chung-Tao, N. Tobias Jacobson +13
Engineering · Physics and Astronomy · #Advancements in Semiconductor Devices and Circuit Design #FOS: Physical sciences #Magnetic properties of thin films #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Quantum and electron transport phenomena
paper · pdf · doi:10.48550/arxiv.1807.01400
openalex publication_date 2018/07/03 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/28
Gate-controllable spin-orbit coupling is often one requisite for spintronic devices. For practical spin field-effect transistors, another essential requirement is ballistic spin transport, where the spin precession length is shorter than the mean free path such that the gate-controlled spin precession is not randomized by disorder. In this letter, we report the observation of a gate-induced crossover from weak localization to weak anti-localization in the magneto-resistance of a high-mobility two-dimensional hole gas in a strained germanium quantum well. From the magneto-resistance, we extract the phase-coherence time, spin-orbit precession time, spin-orbit energy splitting, and cubic Rashba coefficient over a wide density range. The mobility and the mean free path increase with increasing hole density, while the spin precession length decreases due to increasingly stronger spin-orbit coupling. As the density becomes larger than ∼6× 1011cm-2, the spin precession length becomes shorter than the mean free path, and the system enters the ballistic spin transport regime. We also report here the numerical methods and code developed for calculating the magneto-resistance in the ballistic regime, where the commonly used HLN and ILP models for analyzing weak localization and anti-localization are not valid. These results pave the way toward silicon-compatible spintronic devices.