Valence transition and superconductivity in the extended periodic Anderson model

In this thesis, an extended periodic Anderson model with an additional local Coulomb repulsion U f c between localized f electrons and conduction electrons is investigated by use of the projector-based renormalization method (PRM). First, it is shown that the model in one dimension shows a valence transition, which becomes sharper, when the energy of the f level approaches the Fermi level. The transition becomes also enhanced, when the hybridization V between the localized and conduction electrons decreases, for the case that the total number of electrons is fixed. In the two-dimensional case, one finds a similar valence transition behavior. However, in the valence transition regime also a superconducting phase may occur. To investigate this phase, we start from an Hamiltonian which includes small gauge symmetry breaking fields. We derive renormalization equations, from which the superconducting pairing functions are self-consistently determined. Our analytical and numerical results show that d- wave superconductivity becomes dominant in the valence transition regime. This confirms the suggestion by Miyake that valence fluctuations may lead to superconductivity in the Ce based heavy-fermion systems under high pressure.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Dresden

Year

2009

Author dc:creator

• Phan, Van Nham

Contributors dc:contributor

• Becker, Klaus W.
• Fehske, Holger
• Brenig, Wolfram

• Valence transition
• unconventional superconductivity
• heavy fermion systems
• extended periodic Anderson model
• Valenzübergang
• unkonventionelle Supraleitung
• Schwerfermionensysteme
• erweitertes periodisches Anderson-Modell