Sökning: "Hubbard Model"
Visar resultat 1 - 5 av 36 avhandlingar innehållade orden Hubbard Model.
1. Correlated materials : models and methods
Sammanfattning : This thesis encompass a series of studies on methods and models for electron systems with local interactions, relevant for correlated materials. The first study focus on the canonical model for local correlation, the Hubbard model. LÄS MER
2. Cluster model of disordered systems : application to doped semiconductors and a simple model polymer
Sammanfattning : In this thesis we study with an extended cluster model calculation the combined effect of disorder and electron-electron interaction on the electronic structure of doped semiconductors and a simple model polymer chain. First a one-band model using a Hartree calculation is compared to other authors result for the impurity band using less realistic Hamiltonians. LÄS MER
3. Theoretical Developments for the Real-Time Description and Control of Nanoscale Systems
Sammanfattning : In this thesis we focus on improvements of the description of the electron-electron correlation effects in nonequilibrium nanosystems. We mainly focus on developments of two nonequilibrium methods, namely the formalism of Nonequilibrium Green’s Function and Time Dependent Density Functional Theory and we explore the possibility to improve existing approximations in these theories. LÄS MER
4. Order in Strongly Correlated Quasi-One-Dimensional Systems : Solving Higher-Dimensional Systems Combining Matrix-Product-State Methods and Mean-Field Theory
Sammanfattning : Since their discovery the understanding of unconventional superconductors (USCs) has posed a great challenge in condensed matter physics. One central problem, both of theory and experiment, lies in determining the microscopic origin of electron pairing in such systems. LÄS MER
5. Fermions in two dimensions and exactly solvable models
Sammanfattning : This Ph.D. thesis in mathematical physics concerns systems of interacting fermions with strong correlations. For these systems the physical properties can only be described in terms of the collective behavior of the fermions. LÄS MER