Dokument: Spin-orbit coupling effects, interactions and superconducting transport in nanostructures
| Titel: | Spin-orbit coupling effects, interactions and superconducting transport in nanostructures | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=16805 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20101221-113646-1 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Schulz, Andreas [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Egger, Reinhold [Gutachter] Prof. Dr. Bruß, D. [Gutachter] | |||||||
| Stichwörter: | interactions in low-dimensional quantum systems, quantum wires, carbon nanotubes, spin-orbit coupling, strongly correlated systems, Luttinger liquid, combined effects of spin-orbit coupling and Coulomb interaction in 1D metals, spectral function, RKKY interaction, bosonization, superconducting transport, molecular Josephson-junctions, Josephson junction coupled to two-level system, conformational degree of freedom, pi-junction, Andreev bound states, dissipationless switching | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 530 Physik | |||||||
| Beschreibung: | In the present thesis we study the electronic properties of several
low dimensional nanoscale systems. In the first part, we focus on the combined effect of spin-orbit coupling (SOI) and Coulomb interaction in carbon nanotubes (CNTs) as well as quantum wires. We derive low energy theories for both systems, using the bosonization technique and obtain analytic expressions for the correlation functions that allow us to compute basically all observables of interest. We first focus on CNTs and show that a four channel Luttinger liquid theory can still be applied when the combined effects of SOI and Coulomb interaction are taken into account. Compared to previous formulations, the low-energy Hamiltonian is characterized by different Luttinger parameters and plasmon velocities. Notably, the charge and spin modes are coupled. Our theory allows us to compute an asymptotically exact expression for the spectral function of a metallic carbon nanotube. We find modifications to the previously predicted structure of the spectral function that can in principle be tested by photoemission spectroscopy experiments. We develop a very similar low energy description for an interacting quantum wire subject to Rashba spin-orbit coupling (RSOC). We derive a two component Luttinger liquid Hamiltonian in the presence of RSOC, taking into account all e-e interaction processes allowed by the conservation of total momentum. The effective low energy Hamiltonian includes an additional perturbation due to intraband backscattering processes with band flip. Within a one-loop RG scheme, this perturbation is marginally irrelevant. The fixed point model is then still a two channel Luttinger liquid, albeit with a non standard form due to SOI. Again, the charge and spin mode are coupled. Using our low energy theory, we address the problem of the RKKY interaction in an interacting Rashba wire. The coupling of spin and charge modes due to SO effects implies several modifications, e.g. the explicit dependence of the power-law decay exponent of the RKKY Hamiltonian on both RSOC and interaction strength and an anisotropic range function. The second part of this thesis is devoted to the study of superconducting transport in a quantum dot Josephson junctions coupled to a two-level system, which serves as a simple model for a bistable conformational degree of freedom of the connecting single molecule. We first address the limit of weak coupling to the leads and calculate the critical current through the junction perturbatively to lowest non-vanishing order in the tunneling couplings, allowing for arbitrary charging energy U and TLS parameters. We show that the critical current can change by orders of magnitude due to the two-level system. In particular, the PI-junction behavior, generally present for strong interactions, can be completely suppressed. We also study the influence of the Josephson current on the state of the TLS in the regime of weak or vanishing charging energy. Within a wide range of parameters, our calculations predict that the TLS is quite sensitive to a variation of the phase difference across the junction. Conformational changes, up to a a complete reversal, can be induced by varying the phase difference. This allows for the dissipationless control (including switching) of the TLS. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Physik » Theoretische Physik | |||||||
| Dokument erstellt am: | 21.12.2010 | |||||||
| Dateien geändert am: | 19.11.2010 | |||||||
| Promotionsantrag am: | 26.05.2010 | |||||||
| Datum der Promotion: | 07.07.2010 |
