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Many-Body effects in Semiconductor Nanostructures
Stockholm University, Faculty of Science, Department of Physics. (Theoretical Atomic Physics)
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Low dimensional semiconductor structures are modeled using techniques from the field of many-body atomic physics. B-splines are used to create a one-particle basis, used to solve the more complex many-body problems. Details on methods such as the Configuration Interaction (CI), Many-Body Perturbation Theory (MBPT) and Coupled Cluster (CC) are discussed. Results from the CC singles and doubles method are compared to other high-precision methods for the circular harmonic oscillator quantum dot. The results show a good agreement for the energy of many-body states of up to 12 electrons.

Properties of elliptical quantum dots, circular quantum dots, quantum rings and concentric quantum rings are all reviewed. The effects of tilted external magnetic fields applied to the elliptical dot are discussed, and the energy splitting between the lowest singlet and triplet states is explored for varying geometrical properties. Results are compared to experimental energy splittings for the same system containing 2 electrons.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2014. , 44 p.
Keyword [en]
coupled cluster, nanostructure, quantum dot, quantum ring, concentric quantum ring, many body pertubation theory
National Category
Nano Technology Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-102344OAI: oai:DiVA.org:su-102344DiVA: diva2:710070
Presentation
2014-04-25, FA31, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 16:05 (English)
Opponent
Supervisors
Available from: 2014-04-24 Created: 2014-04-02 Last updated: 2014-04-24Bibliographically approved
List of papers
1. Performance of the coupled-cluster singles and doubles method applied to two-dimensional quantum dots
Open this publication in new window or tab >>Performance of the coupled-cluster singles and doubles method applied to two-dimensional quantum dots
2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 3, 035112Article in journal (Refereed) Published
Abstract [en]

An implementation of the coupled-cluster single and double excitations (CCSD) method on two-dimensional quantum dots is presented. Advantages and limitations are studied through comparison with other high accuracy approaches, including another CCSD implementation, for up to twelve confined electrons. The possibility to effectively use a very large basis set is found to be an important advantage compared to full configuration interaction implementations. The error in the ground-state energy introduced by truncating at triple excitations is shown to be comparable to the difference between the results from the variation and diffusion Monte Carlo methods. Convergence of the iterative solution of the coupled cluster equations is found for surprisingly weak confinement strengths even when the full electron-electron interaction is treated as a perturbation. The relevance of the omitted excitations is investigated through comparison with full configuration interaction results. DOI: 10.1103/PhysRevB.87.035112

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-87693 (URN)10.1103/PhysRevB.87.035112 (DOI)000313331900002 ()
Funder
Swedish Research Council
Note

AuthorCount:3;

Available from: 2013-02-15 Created: 2013-02-14 Last updated: 2017-04-28Bibliographically approved
2. Two-electron quantum dot in tilted magnetic fields: Sensitivity to the confinement model
Open this publication in new window or tab >>Two-electron quantum dot in tilted magnetic fields: Sensitivity to the confinement model
Show others...
2013 (English)In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 86, no 10, 430Article in journal (Refereed) Published
Abstract [en]

Semiconductor quantum dots are conventionally treated within the effective-mass approximation and a harmonic model potential in the two-dimensional plane for the electron confinement. The validity of this approach depends on the type of the quantum-dot device as well as on the number of electrons confined in the system. Accurate modeling is particularly demanding in the few-particle regime, where screening effects are diminished and thus the system boundaries may have a considerable effect on the confining potential. Here we solve the numerically exact two-electron states in both harmonic and hard-wall model quantum dots subjected to tilted magnetic fields. Our numerical results enable direct comparison against experimental singlet-triplet energy splittings. Our analysis shows that hard and soft wall models produce qualitatively different results for quantum dots exposed to tilted magnetic fields. Hence, we are able to address the sensitivity of the two-body phenomena to the modeling, which is of high importance in realistic spin-qubit design.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-96095 (URN)10.1140/epjb/e2013-40677-x (DOI)000325608100003 ()
Note

AuthorCount:5;

Available from: 2013-11-14 Created: 2013-11-11 Last updated: 2017-04-28Bibliographically approved

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