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Rashba spin-orbit interaction in 1-dimensional nanowires

Year: 2016
Type: dissertation
Abstract: Now that the first signatures of Majorana zero modes have been ob-\nserved in experiments, a huge effort towards topological quantum com-\nputation is currently underway. Majorana zero modes can appear in\nnanowire systems, with their topological protection depending on the spin-\norbit interaction strength. The spin-orbit interaction strength is therefore\na crucial parameter in this experimental field. The largest contribution is\nexpected to be Rashba spin-orbit interaction, which is the subject of this\nthesis.\nSpin orbit interaction in semiconducting systems is governed by sym-\nmetry. Spin-orbit interaction is forbidden by symmetry if no additional\nsymmetries are broken in [111] InSb nanowires. Upon reducing the spa-\ntial symmetry group, both Dresselhaus and Rashba spin-orbit interaction\ncan emerge in the system. In this thesis a perturbative model for Rashba\nspin-orbit interaction, which occurs when an electric field reduces spatial\nsymmetry, is developed to predict the interaction strength. This model\nis then compared to numerical simulations in quantum well systems per-\nformed with Mathematica and in nanowire simulations performed with\nKwant.\nThe model, incorporating the effect of changing geometric dimensions,\nsubband number and the material, shows good agreement with the numer-\nical simulations. Electrical fields resulting from Schrödinger-Poisson sim-\nulations are then used to induce Rashba spin-orbit interaction in hexago-\nnal nanowire systems similar to experimental devices again matching the\nmodel. Finally, it is shown that the model can be used to calculate re-\nsults which are intractable to calculate via numerical simulations to find\nthe effect of superconducting coverage of the nanowire on the spin-orbit\ninteraction.
Language: English
Open Access status: green
OpenAlex ID: W2313786261
Cites: 28
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Related to: 10