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Visar resultat 1 - 5 av 7 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Ultracold atoms in optical potentials : from noise-induced transport to superfluidity

    Författare :Martin Zelan; Claude Dion; Sile Nic Chormaic; Umeå universitet; []
    Nyckelord :Brownian motors; noise-induced transport; superfluidity; ultracold atoms; optical potentials; optical lattices; laser coooling; fysik; Physics;

    Sammanfattning : In this thesis, both experimental studies and numerical simulations of ultracold atoms in optical potentials are presented in a collection of nine scientific papers. In particular, noise-induced transport in dissipative optical lattices and superfluid properties of Bose-Einstein condensates have been studied. LÄS MER

  3. 2. Superfluidity and Supersolidity in Ultracold Atomic Gases Beyond Mean Field

    Författare :Mikael Nilsson Tengstrand; NanoLund: Centre for Nanoscience; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Bose-Einstein condensation; superfluidity; supersolidity; ultracold atomic gases; dipolar gases; binary Bose mixtures; quantum droplets; beyond mean field; quantum fluctuations; Fysicumarkivet A:2022:Nilsson;

    Sammanfattning : This thesis investigates ultracold bosonic systems using an extended mean-field formalism with a focus on their superfluid and supersolid properties. The dissertation comprises five chapters and four articles, where the chapters provide some background to the research put forward in articles. LÄS MER

  4. 3. Vortices and Persistent Currents in Rotating Bose Gases - a Diagonalization Approach

    Författare :Sara Bargi; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Bose-Einstein condensation; vortices; superfluidity; Fysicumarkivet A:2010:Bargi;

    Sammanfattning : In this thesis, I explore the behavior of rotating ultra-cold Bose gases, by diagonalizing the Hamiltonian. This method has the advantage of being exact in the limit of weak interactions, and thus is a useful complement to the more commonly used Gross-Pitaevskii (GP) equation, which relies on a mean-field approximation. LÄS MER

  5. 4. Bose-Einstein Condensation of Magnetic Excitons in Semiconductor Quantum Wells

    Författare :Vitalie Boţan; Lars Nordström; Sveatoslav Moskalenko; Pavlos Lagoudakis; Uppsala universitet; []
    Nyckelord :Physics; Bose-Einstein condensation; magnetic excitons; electron-hole pairs; electron-hole liquid; magnetorotons; magnetoplasmons; superfluidity; Fysik;

    Sammanfattning : In this thesis regimes of quantum degeneracy of electrons and holes in semiconductor quantum wells in a strong magnetic field are studied theoretically. The coherent pairing of electrons and holes results in the formation of Bose-Einstein condensate of magnetic excitons in a single-particle state with wave vector K. LÄS MER

  7. 5. Phase transitions in novel superfluids and systems with correlated disorder

    Författare :Hannes Meier; Mats Wallin; Asle Sudbø; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; condensed matter physics; phase transitions; critical phenomena; spin models; quantum phase transitions; quantum fluids; superfluidity; superconductivity; disordered systems; Bose glass; dirty bosons; vortex pinning; statistical mechanics; Monte Carlo simulation; Wolff algorithm; classical worm algorithm; Wang-Landau algorithm; Fysik; Physics;

    Sammanfattning : Condensed matter systems undergoing phase transitions rarely allow exact solutions. The presence of disorder renders the situation  even worse but collective Monte Carlo methods and parallel algorithms allow numerical descriptions. LÄS MER