Physical Sciences and Mathematics Commons^™

An Investigation Of Pinning Landscapes With Engineered Defects: Contact-Free Critical Current Density Measurements, John William Sinclair

Doctoral Dissertations

Pinning landscapes in modern second generation coated conductors are excellent candidates for studies of vortex pinning. The ability to produce engineered defects in thin films of high temperature superconductors allows one to investigate representative distinct pinning sites, with the objective of understanding how different pinning centers contribute, compete and evolve under varying conditions of magnetic field strength and orientation, and temperature.New contact-free methods were developed specifically to investigate this system in new ways, especially the dependence of the critical current density Jc on orientation of the magnetic field. A superconducting quantum interference device (SQUID)-based magnetometer was used to determine angular …

Transport And Optical Properties Of Quantized Low-Dimensional Systems, Xiaoguang Li

Doctoral Dissertations

In this thesis, we present a systematic investigation of the static and dynamic response properties of low-dimensional systems, using a variety of theoretical techniques ranging from time dependent density functional theory to the recursive Green's function method.

As typical low-dimensional systems, metal nanostructures can strongly interact with an electric field to support surface plasmons, making their optical properties extremely attractive in both fundamental and applied aspects. We have investigated the energy broadening of surface plasmons in metal structures of reduced dimensionality, where Landau damping is the dominant dissipation channel and presents an intrinsic limitation to plasmonics technology. We show that …

Electronic Excitations In Ytio3 Using Tddft And Electronic Structure Using A Multiresolution Framework, William Scott Thornton

Doctoral Dissertations

We performed ab initio studies of the electronic excitation spectra of the ferro- magnetic, Mott-insulator YTiO3 using density functional theory (DFT) and time- dependent density functional theory (TDDFT). In the ground state description, we included a Hubbard U to account for the strong correlations present within the d states on the cation. The excitation spectra was calculated using TDDFT linear response formalism in both the optical limit and the limit of large wavevector transfer. In order to identify the local d-d transitions in the response, we also computed the density response of YTiO3 using a novel technique where the basis …