Professor Paul Crowell

Project Title: 
Spin Transport and Dynamics

Given the advances in experimental measurements of the spin-related Hall effects in n-GaAs, including both spin Hall effect (SHE) and non-local inverse spin Hall effect (ISHE), and the success in theoretical explanation given by impurity scattering mechanism proposed by Engel et al., the researchers have designed experiments to perform a local-measurement of the ISHE in n-GaAs, doped with Si, at concentrations just above the metal-insulator transition. They have carried out a series of spin transport measurements on Fe/n-GaAs heterostructure samples with different doping (3e16 cm-3 to 7e16 cm-3) and at various temperatures (from 30 K to 110 K).

With data obtained from the experiments, the researchers plan to do numerical modeling to generate theoretical explanations. During 2019, they used the Semiconductor Module of COMSOL to solve Poisson’s equation in a 3D cross-shaped GaAs channel with a rectangular-shaped thin Fe contact on top of it. The top Fe is the current source and two side surfaces are drains, which determines the boundary condition. The researchers find the current density is high near the side edges of the Fe contacts and decrease by 1 order of magnitude vertically along the channel underneath the Fe contact. This helped in calculating anomalous Hall voltage signal along the GaAs channel and the effective spin drift length under the influence of the current distribution. Future work includes similar calculations for the rest of the samples. The researchers also plan to explore the possibility of using COMSOL to solve the spin transport equations to calculate the spin polarization profile which will then be used to calculate the spin Hall voltage measured in the experiments.

Project Investigators

Professor Paul Crowell
Zhen Jiang
 
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