Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"Bose gases"”.
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The dynamics of bose gases
… equations that models the dynamics of Bose gases and arises in the derivation of the cubic and quintic nonlinear Schrödinger equations from an N-body linear Schrödinger equation. In Chapter 2, we consider the cubic case in R³ and derive the GP hierarchy in the strong topology …
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Spin-orbit coupled Bose gases
Quantum simulation is a very active and growing field. Various quantum systems can be used to emulate existing materials in an accurate and controllable way, as well as to generate new states of matter that have not been found in the real world but the existence of which does not contradict the …
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Quenching normal Bose gases to Unitarity
… interactions in three-dimensional thermal Bose gases, with particular emphasis on the unitary regime of maximal interactions. We use 39K, a bosonic isotope, in anisotropic harmonic optical trapping potentials. In the unitary Bose gas we find many-body complexity introduced by the …
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Quasi-condensation in low-dimensional Bose gases
… of the present thesis is the one-dimensional Bose gas. Since long-rang order is destroyed by infra-red fluctuations in one dimension, only the formation of a quasi-condensate is possible, which exhibits suppressed density fluctuations, but whose phase fluctuates strongly. It is shown that …
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Dynamics and thermodynamics of strongly driven Bose gases
This thesis explores ultracold Bose gases trapped in a uniform potential and forced far from equilibrium with a continuous drive. It contains experimental results obtained with a 39K gas, alongside numerical simulations and theoretical modeling. The starting point of the experiments is always an …
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Exploring Interacting Bose Gases in and out of Equilibrium
… experiments that explore interacting ultracold Bose gases, both in and out of equilibrium. Our experiments are performed using a gas of $^{39}$K or $^{87}$Rb confined in the uniform potential of an optical box trap, a novel testbed for quantum many-body phenomena. Our work focuses on weakly …
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Sound Waves and Turbulence in Two-dimensional Bose Gases
… carried out on a two-dimensional (2D) Bose gas cooled down to quantum degeneracy. In the first one we focus on the equilibrium properties of the gas close to the Berezinskii-Kosterlitz-Thouless (BKT) phase transition, while in the second one we study the out-of-equilibrium dynamics of …
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Few- and Many-body Physics with Strongly Interacting Bose Gases
… and many-body physics in strongly interacting Bose gases. Our experimental platform uses Bose-Einstein condensates and cold thermal gases of 39K in different hyperfine states or their combinations, trapped in a quasi-uniform optical potential. We focus on the regime of strong interatomic …
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Direct and inverse turbulent cascades in a 2D Bose gas
… explores the dynamics of two-dimensional (2D) Bose gases driven far from equilibrium, as well as their subsequent relaxation dynamics, and can be divided into two sections. The first one provides the background for the novel work of the second part, which describes three experimental studies. …
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Crystalline and glassy states of ultracold atomic systems
… as we show, the crystallization transition for a Bose-Einstein condensate in a multimode cavity is driven first-order by fluctuations, through the Brazovskii effect. The ordered state to which this crystallization transition gives rise is a ""supersolid,"" possessing both superfluid and solid …
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Atomlaser und Phasenkohärenz atomarer Bose-Einstein-Kondensate
… Auskopplung von Atomen aus einem atomaren Bose-Einstein-Kondensat berichtet. Es wurde so eine kohärente Strahlquelle für Materiewellen entwickelt, die aufgrund ihrer Analogie zu der Erzeugung von Licht in einem Laser als Atomlaser bezeichnet wird. In einer neu entwickelten magnetischen …
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Super-resolution Control of Ultracold Dipolar Atoms on a 50-nm Scale
Degenerate quantum gases of magnetic atoms such as dysprosium (Dy) and erbium (Er) offer new opportunities to quantum simulation research due to their large spin degree of freedom and long-range dipole-dipole interactions. In this thesis, following an introduction to the fundamental properties of …
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Quantum Monte Carlo simulations of electrons and holes
… bound states of an electron and a hole, and obey Bose statistics. A low density exciton gas is an experimentally realizable dilute Bose gas. The scattering length a8 of a dilute Bose gas determines its properties, but is difficult to calculate. We present an essentially exact QMC treatment of …
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Observing the 2D Bose glass in an optical quasicrystal
… state of non-interacting and weakly interacting Bose gases in a 2D quasicrystalline lattice. The second experiment is mainly performed in the non-interacting limit, in which we probe the localisation transition by employing triangular lattice pulses and studying the time scale required for …
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Ultracold quantum gases in three-dimensional optical lattice potentials
… in the many body physics of ultracold atomic gases. A Bose-Einstein condensate is loaded into a three-dimensional optical lattice potential formed by a standing wave laser light field. In this novel quantum system we have been able to both realize a quantum phase transition from a superfluid …
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Out-of-equilibrium dynamics in a tuneable homogeneous Bose gas
… dynamics in an interacting homogeneous Bose gas. We use the versatile platform of an ultracold gas of $^{39}$K, prepared in an optical box trap. The experiment features both tuneable interaction strengths and a homogeneous atomic density. We examine first a weakly interacting …
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Superfluidity in a uniform two-dimensional Bose gas
… in both liquid helium and ultracold atomic gases, is the existence of two kinds of sound excitations, the first and second sound. Unlike its three dimensional counter-part, however, superfluidity in two dimensions is associated with the pairing of vortices of opposite circulation as …
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Tuneable homogeneous Bose fluids close to and far from equilibrium
… experiments with an ultracold weakly interacting Bose gas of 39 K in a 3- dimensional homogeneous optical trap. We expound three phenomena in different regimes from adiabatic equilibrium to ‘true’ far-from-equilibrium. We first outline a cooling effect driven by three-body recombination, which has …