Search for dissertations about: "lattice dynamics"

Showing result 16 - 20 of 128 swedish dissertations containing the words lattice dynamics.

  2. 16. Theoretical studies of lattice- and spin-polarons

    Author : Nina Bondarenko; Olle Eriksson; Natalia Skorodumova; Manuel Pereiro; Maria Roser Valenti Vall; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Polaron; Nonlinear Schrödinger Equation; Nonlocality; Solitons; Integrable systems; Quantum field theory low energy ; Electron-phonon interaction; Density functional theory; Electronic structure of atoms and molecules; Spin-polaron; Langevin equation; Transport properties; Hubbard model; Heisenberg lattice; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Abstract : Theoretical studies of lattice- and spin-polarons are presented in this thesis, where the primary tool is ab-initio electronic structure calculations. The studies are performed with employment of a variety of analytical and computational methods. READ MORE

  4. 17. Multi-Meson Dynamics in Chiral Perturbation Theory

    Author : Mattias Sjö; Partikel- och kärnfysik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Spridningsamplituder; Effektiv Fältteori; Spontant symmetribrott; Ickelinjära sigmamodellen; Kirala Lagrangianer; Hadronspektroskopi; Strukturer och Interaktioner; Gitter-QCD; Scattering amplitudes; Effective Field Theories; Spontaneous Symmetry Breaking; Nonlinear sigma model; Chiral Lagrangians; Hadronic Spectroscopy; Structure and Interactions; Lattice QCD;

    Abstract : This thesis concerns scattering of light mesons in the case where the number of external particles exceeds four (that is, three or more particles in the initial or final state), calculated using chiral perturbation theory.This is both of theoretical interest in the study of scattering amplitudes, and relevant for systems of three or more pions simulated using lattice quantum chromodynamics. READ MORE

  5. 18. Ultrafast spin dynamics and relaxation in metallic ferromagnets

    Author : Vivek Unikandanunni; Stefano Bonetti; Olof Karis; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Magnetization dynamics; Three temperature model; Cobalt; Anisotropy; Electron-phonon coupling; THz; Platinum; Silver; fysik; Physics;

    Abstract : We performed ultrafast demagnetization measurements on epitaxial hcp-cobalt thin film with the easy axis in the plane of the film by pumping the sample with 400 nm radiation and probing the magneto-optic effects in the longitudinal magneto optic Kerr effect geometry using 800 nm radiation. The in-plane magnetic anisotropy of the sample enabled us to measure the demagnetization dynamics along two different crystalline directions, namely along the easy axis and at 45 degrees between the easy and hard axes. READ MORE

  6. 19. Water Relaxation Processes as Seen by NMR Spectroscopy Using MD and BD Simulations

    Author : Ken Åman; Per-Olof Westlund; Arnold Maliniak; Umeå universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Physical chemistry; NMR; Stochastic Liouville Equation; Brownian Dynamics; Molecular Dynamics; Water; Relaxation; Deuterium; ESR; Fysikalisk kemi; Physical chemistry; Fysikalisk kemi; Physical Chemistry; fysikalisk kemi;

    Abstract : This thesis describes water proton and deuterium relaxation processes, as seen by Nuclear Magnetic Resonance (NMR) spectroscopy, using Brownian Dynamics (BD) or Molecular Dynamics (MD) simulations. The MD simulations reveal new detailed information about the dynamics and order of water molecules outside of a lipid bilayer. READ MORE

  7. 20. Optical Spectroscopy on Correlated Electron Materials

    Author : Johan Bielecki; Chalmers tekniska högskola; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; dynamics; optical spectroscopy; colossal magnetoresistance; magnetism; transition metal oxides; high temperature superconductivity;

    Abstract : Strongly correlated materials poses a great challenge to our microscopic understanding of matter, mainly due to the inability of perturbative methods to predict the properties of such materials. This inability stems from strong correlations between electronic, lattice and spin degrees of freedom, leading to a variety of complex and exotic phenomena such as (unconventional) superconductivity, metal-insulator transitions, non-Fermi liquid behavior and colossal magnetoresistance. READ MORE