Sökning: "hubbard"

Visar resultat 21 - 25 av 50 avhandlingar innehållade ordet hubbard.

1. 21. Non-Linear Canonical Methods in Strongly Correlated Electron Systems

   Författare :Matteo Bazzanella; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Majorana fermions; Emergent Majorana fermions; Non-linear transformation; canonical transformation; Kondo lattice; Mott insulator; Mean-field; Path-integral;

   Sammanfattning : In this thesis some new ideas to perform the analysis of Strongly Correlated Electronic Systems (SCES) are developed. In particular the use of non-linear canonical transformations is considered thoroughly. LÄS MER

3. 22. Role of charge and spin fluctuations and their interplay in solids : A Green’s function approach

   Författare :Tor Sjöstrand; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Green’s function; correlations; collective excitations; screened interaction; electric polarization; orbital and spin magnetization; magnon-phonon interaction; Fierz ambiguity; time-dependent exchange-correlation potential;

   Sammanfattning : Due to the large number of electrons, solid state physics boils down to many-body approximations in which only selected types of collective excitations are taken into account, guided by the emergent properties of the material under study. In this thesis, the collective excitations of primary interest are electronic charge and spin fluctuations(plasmons and magnons) and nuclear charge fluctuations (phonons). LÄS MER

4. 23. Correlated Electronic Structure of Materials : Development and Application of Dynamical Mean Field Theory

   Författare :Patrik Thunström; Olle Eriksson; Alexander Lichtenstein; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; DFT; DMFT; correlation; entanglement; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

   Sammanfattning : This thesis is dedicated to the development, implementation and application of a combination of Density Functional Theory and Dynamical Mean Field Theory. The resulting program is shown through several examples to be a powerful and flexible tool for calculating the electronic structure of strongly correlated materials. LÄS MER

5. 24. Many-photon effects in time-resolved second harmonic generation from systems in optical cavities

   Författare :Megha Gopalakrishna; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Second harmonic generation; Cavity optics; Non-linear optics; Cavity leakage; Ultracold atoms; Dicke model; Exact diagonalization; Non-equilibrium Green s functions; Fysicumarkivet A:2024:Gopalakrishna;

   Sammanfattning : Second harmonic generation is popular due to its numerous applications in different technologies dealing with multiple fields of science. The rapid technical advancement with the second harmonic generation demands parallel development in the theoretical understanding. LÄS MER

7. 25. Nanospintronics with Molecular Magnets - Tunneling and Spin-Electric Coupling

   Författare :Javier Francisco Nossa Márquez; Fasta tillståndets fysik; []
   Nyckelord :Molecular magnets; spin exchange; spin-orbit interaction; magnetic anisotropy; spin frustration; spin chirality; spin-electric control; quantum transport; Coulomb blockade; density functional theory; quantum master equation.;

   Sammanfattning : This dissertation investigates theoretically electric control of the magnetic properties of molecular magnets. Two classes of magnetic molecules are considered. The first class consists of molecules that are spin frustrated. LÄS MER