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A Variational Cluster Approximation for the Heisenberg Model

dc.contributor.advisorKehrein, Stefan Prof. Dr.
dc.contributor.authorFilor, Stephan
dc.date.accessioned2017-04-13T08:46:20Z
dc.date.available2017-04-13T08:46:20Z
dc.date.issued2017-04-13
dc.identifier.urihttp://hdl.handle.net/11858/00-1735-0000-0023-3E15-1
dc.identifier.urihttp://dx.doi.org/10.53846/goediss-6255
dc.identifier.urihttp://dx.doi.org/10.53846/goediss-6255
dc.language.isoengde
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc530de
dc.titleA Variational Cluster Approximation for the Heisenberg Modelde
dc.typedoctoralThesisde
dc.contributor.refereeKehrein, Stefan Prof. Dr.
dc.date.examination2016-10-17
dc.subject.gokPhysik (PPN621336750)de
dc.description.abstractengIn this thesis we present a novel variational cluster approximation for Heisenberg spin systems. It is based on the self-energy functional theory by Potthoff for fermionic and bosonic models with local interactions. To develop a similar method for spin systems, we derive a free energy functional which is the starting point of the approximation. Within this approximation, we find an analytical expression to evaluate the free energy by tiling the real system into a set of clusters. We describe the technical details of the spin variational cluster approximation and the evaluation of the free energy. The method is tested for the antiferromagnetic spin-1/2 Heisenberg chain with first- and second-neighbour interactions. Thereby, we investigate the dependence of the approximation on cluster size and the choice of variational parameters. The opportunities and limitations as well as future applications of the method are thoroughly discussed.de
dc.contributor.coRefereeHonecker, Andreas Prof. Dr.
dc.subject.engHeisenberg modelde
dc.subject.engVariational Cluster Approximationde
dc.subject.engSpin systemde
dc.identifier.urnurn:nbn:de:gbv:7-11858/00-1735-0000-0023-3E15-1-4
dc.affiliation.instituteFakultät für Physikde
dc.identifier.ppn884521958


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