Thesis
One-dimensional quantum transport phenomena in periodically modulated electron waveguides
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T17057
- Person Identifier (Local)
- 201889178
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The study of quantum transport in one dimension is of great interest in many areasof condensed matter physics. This thesis is motivated by conductance measurementsin modulated LAO/STO nanowires, where a strong conductance baseline of 2e2/h isobserved when a Kronig-Penney potential is applied, which survives up to externalmagnetic fields > 18 T. This is also observed when the nanowire is helically modulated, but an additional feature is the appearance of conductance oscillations abovethe 2e2/h baseline which occur at lower energies than the 4e2/h peak.In order to model this, we begin by constructing an electron waveguide modelfor the nanowire formed at the LAO/STO interface. We then include the effect ofperiodic modulations and associated spin-orbit coupling resulting from these, andanalyse the resulting band structure and conductance, finding that a single electronmodel is not sufficient to explain the 2e2/h baseline. This was found in previouswork, and the solution is to include electron-electron interactions.To include the effects of these, we begin with a standard BCS-like mean-fieldmodel. To study first the effect coming from a periodic modulation of the potentialin the waveguide (vertical modulation), we introduce only the associated spin-orbitcoupling to this model. We find that this leads to enhanced pairing, and couldpotentially explain the strong baseline of 2e2/h. Additionally, we look only at theeffect of a periodic modulation in the centre of the nanowire (lateral modulation),which we find introduces triplet pairing in the waveguide region.Combining these two modulations together, we extend the mean-field model againto include the form of the modulation potential alongside associated spin-orbit couplings to study the helical waveguide. We observe enhanced pairing and tripletpairing simultaneously. To study the oscillations in conductance, we introduce aphenomenological pair scattering model where triplet pairs incedent on the interfacebetween helical and unmodulated regions can backscatter. We find that this modelcan indeed produce oscillations above the 2e2/h baseline.
- Advisor / supervisor
- Daley, Andrew
- Resource Type
- DOI
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PDF of thesis T17057 | 2024-10-02 | Public | Download |