Hole spins in GE-SI nanowires

M. Brauns

    Research output: ThesisPhD Thesis - Research UT, graduation UT

    195 Downloads (Pure)

    Abstract

    In a universal quantum computer, coherent control over the state of a quantum mechanical two-level system is needed. This requires interactions of the quantum state with its environment. Inherently, such interactions also lead to decoherence and thus limit the performance of the quantum computer. A profound knowledge of the relevant interaction mechanisms is therefore key to the realization of a quantum computer. In this thesis we use Ge-Si core-shell nanowires to investigate holes confined to one dimension. Mixing of heavy and light hole states leads to a strong, anisotropic spin-orbit interaction in this system. We define highly stable quantum dots of different lengths in the nanowire and controllably split up longer quantum dots into double quantum dots. The effective g-factor in these one-dimensional hole quantum dots is found to be highly anisotropic with respect to the nanowire axis as well as the electric-field axis. In double quantum dots, we observe shell filling of new orbitals and Pauli spin blockade of the second hole entering the orbital. The leakage current in the spin-blocked state is highly anisotropic with spin-flip cotunnelling as the dominant leakage mechanism. At finite magnetic fields, we also find signatures of leakage current induced by spin-orbit coupling and anisotropic Coulomb effects.
    Original languageUndefined
    Awarding Institution
    • University of Twente
    Supervisors/Advisors
    • van der Wiel, Wilfred Gerard, Supervisor
    • Zwanenburg, Floris Arnoud, Advisor
    Thesis sponsors
    Award date24 Mar 2016
    Place of PublicationEnschede
    Publisher
    Print ISBNs978-90-365-4082-7
    DOIs
    Publication statusPublished - 24 Mar 2016

    Keywords

    • METIS-316214
    • EWI-27016
    • IR-100012

    Cite this

    Brauns, M. (2016). Hole spins in GE-SI nanowires. Enschede: Universiteit Twente. https://doi.org/10.3990/1.9789036540827
    Brauns, M.. / Hole spins in GE-SI nanowires. Enschede : Universiteit Twente, 2016. 82 p.
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    Brauns, M 2016, 'Hole spins in GE-SI nanowires', University of Twente, Enschede. https://doi.org/10.3990/1.9789036540827

    Hole spins in GE-SI nanowires. / Brauns, M.

    Enschede : Universiteit Twente, 2016. 82 p.

    Research output: ThesisPhD Thesis - Research UT, graduation UT

    TY - THES

    T1 - Hole spins in GE-SI nanowires

    AU - Brauns, M.

    PY - 2016/3/24

    Y1 - 2016/3/24

    N2 - In a universal quantum computer, coherent control over the state of a quantum mechanical two-level system is needed. This requires interactions of the quantum state with its environment. Inherently, such interactions also lead to decoherence and thus limit the performance of the quantum computer. A profound knowledge of the relevant interaction mechanisms is therefore key to the realization of a quantum computer. In this thesis we use Ge-Si core-shell nanowires to investigate holes confined to one dimension. Mixing of heavy and light hole states leads to a strong, anisotropic spin-orbit interaction in this system. We define highly stable quantum dots of different lengths in the nanowire and controllably split up longer quantum dots into double quantum dots. The effective g-factor in these one-dimensional hole quantum dots is found to be highly anisotropic with respect to the nanowire axis as well as the electric-field axis. In double quantum dots, we observe shell filling of new orbitals and Pauli spin blockade of the second hole entering the orbital. The leakage current in the spin-blocked state is highly anisotropic with spin-flip cotunnelling as the dominant leakage mechanism. At finite magnetic fields, we also find signatures of leakage current induced by spin-orbit coupling and anisotropic Coulomb effects.

    AB - In a universal quantum computer, coherent control over the state of a quantum mechanical two-level system is needed. This requires interactions of the quantum state with its environment. Inherently, such interactions also lead to decoherence and thus limit the performance of the quantum computer. A profound knowledge of the relevant interaction mechanisms is therefore key to the realization of a quantum computer. In this thesis we use Ge-Si core-shell nanowires to investigate holes confined to one dimension. Mixing of heavy and light hole states leads to a strong, anisotropic spin-orbit interaction in this system. We define highly stable quantum dots of different lengths in the nanowire and controllably split up longer quantum dots into double quantum dots. The effective g-factor in these one-dimensional hole quantum dots is found to be highly anisotropic with respect to the nanowire axis as well as the electric-field axis. In double quantum dots, we observe shell filling of new orbitals and Pauli spin blockade of the second hole entering the orbital. The leakage current in the spin-blocked state is highly anisotropic with spin-flip cotunnelling as the dominant leakage mechanism. At finite magnetic fields, we also find signatures of leakage current induced by spin-orbit coupling and anisotropic Coulomb effects.

    KW - METIS-316214

    KW - EWI-27016

    KW - IR-100012

    U2 - 10.3990/1.9789036540827

    DO - 10.3990/1.9789036540827

    M3 - PhD Thesis - Research UT, graduation UT

    SN - 978-90-365-4082-7

    PB - Universiteit Twente

    CY - Enschede

    ER -

    Brauns M. Hole spins in GE-SI nanowires. Enschede: Universiteit Twente, 2016. 82 p. https://doi.org/10.3990/1.9789036540827