Spin and Other Electronic Properties of InSb Quantum Wells

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This project addresses electron spin properties and ballistic transport effects in InSb quantum wells, and aims to optimize such structures for applications that rely on these phenomena. Large spin effects such as the Rashba and Zeeman terms are correlated with narrow band gaps. Because InSb has the smallest band gap of any III-V semiconductor, spin effects are expected to be amongst the largest. The approach involves a range of experiments to study these effects in InSb heterostructures. First, energy splitting due to the Rashba effect will be probed using an electron spin resonance technique. By varying the structural parameters of the quantum well, factors that influence the Rashba effect will be identified. This is expected to contribute to a more complete understanding of the Rashba effect with the goal of optimizing structures for large Rashba split-ting. Second, point-contact techniques for studying spin splitting in 1D channels will be ex-plored. In these 1D channels the Rasbha effect has been predicted to lead to a much richer con-ductance spectra. InSb is well suited to this study due to both the large Rashba term and the small effective mass that leads to large confinement energies. Third, quantum Hall ferromagnets will be sought by exploiting the large Zeeman effect in InSb. Studies of ferromagnetism in quantum fluids may improve understanding of ferromagnetism in general. Lastly, a newly proposed spin filter that takes advantage of the large Zeeman effect will be developed. Experiments on the bal-listic transport properties of InSb quantum wells will be performed. The small effective mass of InSb leads to long mean free paths. Preliminary data suggests ballistic transport even at 185K. Although unrelated to spin, ballistic transport is required for some spin devices. It is planned to develop structures that exhibit ballistic transport at room temperature and structures that have low-temperature mean free paths sufficiently long for electron focusing experiments. Continued improvement in the quality of heterostructures will be aided by ongoing excitonic studies which provide values of materials parameters important for device design. %%% The project addresses fundamental research issues in areas of electronic materials science having technological relevance. An important feature of the project is the strong emphasis on education, and the integration of research and education. This research effort enlists contributions from un-dergraduates, graduate students, and postdocs. These experiences will contribute to the prepara-tion of students and staff for employment in areas of technologically importance. The combined resources of collaborations among the PI and two co-PIs provide special opportunities for educa-tion and training in highly interdisciplinary forefront research.***