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Observation of a Persistent Non-Equilibrium State in an Extremely Isotropic Harmonic Potential

TitleObservation of a Persistent Non-Equilibrium State in an Extremely Isotropic Harmonic Potential
Publication TypeThesis
Year of Publication2015
AuthorsLobser, DS
Academic DepartmentPhysics
DegreePh. D.
Number of Pages139
Date Published07-2015
UniversityUniversity of Colorado
CityBoulder, CO

Ludwig Boltzmann made tremendously important contributions to the problem of connecting macroscopic, empirical phenomena with microscopic, atomistic dynamics. At the end of the nineteenth century, Boltzmann was confronted with various strong objections to his work. For example, Boltzmann's atomistic explanations presuppose the reality of atoms, a notion that was vigorously rejected in some circles [14, 38]. Then too, there was the critique by Loschmidt that Boltzmann's H-theorem, put forth as a microscopic explanation for the Second Law of Thermodynamics, could hardly account for irreversible physics when the individual two-atom collisions were each reversible [18, 42]. Still intriguing today is the existence of special cases of the Boltzmann equation in which time-varying distributions of atoms resist the imperative of equilibration, even in the presence of collisions. Boltzmann discussed such situations in a paper dedicated to responding to Loschmidt's critique [7, 4]. Perhaps Boltzmann's motivation was to enumerate special cases where his famous H value does not relax as it should, and by enumerating them, point out their nonnaturalness, their artificiality. Damping, or relaxation to equilibrium, of a time-invariant phase-space distribution, is an all-but universal result predicted by the Boltzmann equation.

Such improbable systems of atoms have only very recently been realized experimentally. Kinoshita et al. [36] experimentally confirmed that atoms constrained to move in a quasi one-dimensional potential, an atomistic Newton's cradle, exhibit vastly suppressed relaxation. Chevy et al. [15] observed long-lived breathe-mode oscillations in highly elongated, but still 3D, geometries. Perhaps one of the more interesting cases is the vanishing damping of the monopole breathe-mode oscillation in a spherically symmetric harmonic oscillator [29], where a cloud of atoms experiences undamped temperature oscillations, causing the cloud to expand and contract as if it were breathing. Until now, this phenomenon has been experimentally inaccessible due to the difficulty in generating isotropic harmonic confinement. This thesis discusses a new magnetic trap capable of producing spherical confinement and presents the first experimental realization of this historically significant oddity using a magnetically trapped gas of 87Rb atoms.