Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.
Campus-Only Access for Five (5) Years
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Gregory M. Grason
Condensed Matter Physics | Statistical, Nonlinear, and Soft Matter Physics
This dissertation consists of two parts. In the first part, we studied the ground state configurations of vortices with multi-scale inter-vortex interactions in layered superconductors. We found that by tuning the multi-scale interaction length, we could create vortex lattice ground states with different symmetries. It has been proposed that these structures can trap ultra-cold atoms for use in quantum emulators. In further work, we measured the phase diagram and discovered many new phases by changing the relative magnitude of the interaction ranges.
In the second part, we analyzed the ground state configurations of confined filaments with long-range repulsive interactions. We first studied only straight filaments, using continuum limit analysis and numerical simulations, and we developed a new microscopic theory of defects. We found that in our system the gradient of the nonuniform density distribution can be controlled not only by the nature of the confinement but also by the range of the repulsive interactions. We also found that in this system, positive defects are much more difficult to create than negative defects. Furthermore, we showed that by using the local isotropic assumption, one can derive the relationship between nonuniform density and topological defects.
In further work, we added a twist to the filament bundles. Generally speaking, uniform filament bundles do not form stable twist states. However, things change when we add defects into the center of the system. The filament bundles with negative disclinations will never form stable twist states, but there is a stable twisted filament bundle when there are positive disclinations. Furthermore, we generalized the local isotropic assumption to the twisted filament system and found a relationship between the nonuniform density, topological defects, and Gaussian curvature.
Meng, Qingyou, "Complex ground states of vortices and filaments" (2018). Doctoral Dissertations. 1282.
Available for download on Monday, May 11, 2020