Sökning: "2D XY model"

Hittade 4 avhandlingar innehållade orden 2D XY model.

  1. 1. Vortex fluctuations in superconductors

    Författare :Peter Olsson; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Superconductor; Two dimensions; vortex; coulomb gas; XY model; Kosterlitz-Thouless transition; high-Tc.;

    Sammanfattning : The vortex fluctuations have proved to be responsible for the onset of dissipation in thin type-II superconducting Aims. There is also growing evidence that dissipation in high- temperature superconductors exhibits the same kind of two-dimensional (2D) behavior. LÄS MER

  3. 2. Critical Phenomena and Exchange Coupling in Magnetic Heterostructures

    Författare :Martina Ahlberg; Gabriella Andersson; Björgvin Hjörvarsson; Steve Bramwell; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; phase transitions; critical behavior; 2D XY model; MOKE; magnetic thin films and superlattices; amorphous multilayers; magnetic proximity effects; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Sammanfattning : The continuous phase transition in thin magnetic films and superlattices has been studied using the magneto-optical Kerr effect (MOKE) and polarized neutron scattering (PNR).  It has been shown that the critical behavior of amorphous thin films belonging to the 2D XY universality class can be described within the same theory as crystalline sample. LÄS MER

  4. 3. Characteristic properties of two-dimensional superconductors close to the phase transition in zero magnetic field

    Författare :Kateryna Medvedyeva; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Fysik; superconductor; two dimensions; phase transition; vortex; currentvoltage characteristics; complex conductivity; scaling; critical exponents; XY-type models; dynamics; Physics; Fysik; fysik; Physics;

    Sammanfattning : The main focus of this thesis lies on the critical properties of twodimensional (2D) superconductors in zero magnetic field. Simulations based on variants of the 2D XY model are shown to give characteristic features close to the phase transition which agree qualitatively with experimental data. LÄS MER

  5. 4. Superfluid Phase Transitions in Disordered Systems

    Författare :Hannes Meier; Mats Wallin Wallin; Peter Olsson; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : This thesis presents results from large scale Monte Carlo simulations of systems subject to a superfluid phase transition in the presence of disorder. The simulations are performed by state-of-the-art, collective Monte Carlo algorithms treating phase degrees of freedom in effective models with amplitude fluctuations integrated out. LÄS MER