73.23.Ra Persistent currents
Refine
Year of publication
- 2005 (1)
Document Type
- Doctoral Thesis (1)
Language
- English (1)
Has Fulltext
- yes (1)
Is part of the Bibliography
- no (1)
Keywords
- Eindimensionaler Leiter (1)
- Fermionensystem (1)
- Heisenberg-Modell (1)
- Magnetoelektronik (1)
- Renormierungsgruppe (1)
Institute
- Physik (1)
The challenging intricacies of strongly correlated electronic systems necessitate the use of a variety of complementary theoretical approaches. In this thesis, we analyze two distinct aspects of strong correlations and develop further or adapt suitable techniques. First, we discuss magnetization transport in insulating one-dimensional spin rings described by a Heisenberg model in an inhomogeneous magnetic field. Due to quantum mechanical interference of magnon wave functions, persistent magnetization currents are shown to exist in such a geometry in analogy to persistent charge currents in mesoscopic normal metal rings. The second, longer part is dedicated to a new aspect of the functional renormalization group technique for fermions. By decoupling the interaction via a Hubbard-Stratonovich transformation, we introduce collective bosonic variables from the beginning and analyze the hierarchy of flow equations for the coupled field theory. The possibility of a cutoff in the momentum transfer of the interaction leads to a new flow scheme, which we will refer to as the interaction cutoff scheme. Within this approach, Ward identities for forward scattering problems are conserved at every instant of the flow leading to an exact solution of a whole hierarchy of flow equations. This way the known exact result for the single-particle Green's function of the Tomonaga-Luttinger model is recovered.