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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 20 of 21 for “"Bose gas"”.
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Superfluidity in a uniform two-dimensional Bose gas
… regarding superfluidity in a two-dimensional gas of ultracold atoms trapped in a uniform potential. It is conceptually divided into three parts. In the first part we offer a theoretical discussion of a superfluid, first from a general perspective and then concentrating on its distinct features …
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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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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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Relaxation of interacting Stark-localized states in a thermal lattice Bose gas
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-12-04 without embargo terms
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Measurement of the density profile of quantized vortices and of the equation of state in a 3D interacting Bose gas
… the analysis of spatial structures in a Bose Einstein condensate. Ultracold atomic gases offer a privileged platform for such kind of experiments, thanks to the fine control that can be achieved on the system’s parameters and to the availability of advanced imaging schemes allowing for a …
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Theory of Quantum Degenerate Gases
… on the transition temperature of a dilute Bose gas; second, the connection between broken non-gauge symmetries and the appearance of multiple condensates in a Bose gas; third, the role of thermally activated ""phase slip"" events in destroying superfluidity near the critical temperature of …
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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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Impurities in a Bose-Einstein condensate using quantum Monte-Carlo methods: ground-state properties.
… properties of impurities immersed in a dilute Bose gas at zero temperature using quantum Monte-Carlo methods. The interactions between bosons are modeled by a hard sphere potential with scattering length a, whereas the interactions between the impurity and the bosons are modeled by a …
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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 …
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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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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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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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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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Aspects of Quantum Fluctuations under Time-dependent External Influences
… Afterwards, we turn our attention towards Bose-Einstein condensates, a laboratory system. Since most of our calculations are performed using a mean-field expansion, we will study the accuracy of a finite-range interaction potential onto such an expansion. Exploiting the universality of …
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Localization and spreading of matter waves in disordered potentials
… connection of our findings with ultracold atomic gases experiments. We concentrate on two main issues: the interplay between localization and interaction in disordered systems and the problem of localization in correlated random potentials. The first problem is investigated considering the …
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Enhanced light-atom interaction in an optical resonator
… state known as a super-TonksƯGirardeau (sTG) gas. We calibrate for the first time the two-body and three-body short-range correlations of the gas. Compared to a three-dimensional non-interacting Bose gas, the g(2) and g(3) correlations of the sTG gas are reduced by a factor of 5 and 130, …
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Topics in the Theory of Quantum Degenerate Gases
… Josephson Effect between two spatially separated Bose-Einstein condensates of atoms each of which can be in two hyperfine states. We derive simple equations of motion for this system closely analogous to the Bloch equations. We also map the dynamics of the system onto those of a classical particle …
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Topics in the theory of quantum degenerate gases
… Josephson Effect between two spatially separated Bose-Einstein condensates of atoms each of which can be in two hyperfine states. We derive simple equations of motion for this system closely analogous to the Bloch equations. We also map the dynamics of the system onto those of a classical particle …
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Tunneling in Degenerate Atomic Gases
The experimental achievement of Bose-Einstein condensation in cold alkali atomic gases in 1995 has started a period of fertile research at the intersection of atomic physics, quantum optics, and condensed matter. In this thesis, various tunneling effects in both bosonic and fermionic gases are …
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Properties of rotating ultracold bosonic quantum gases
… properties of ultracold bosonic quantum gases in two trapped configurations, a quasi-two-dimensional gas in a harmonic trap and a quasi-one-dimensional gas in a toroidal trap. First, we investigate the effects of correlations on the properties of the ground state of the rotating …
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