Physics Commons^™

Macromolecular Structure Determination At X-Ray Free Electron Lasers From Single-Particle Imaging To Time-Resolved X-Ray Crystallography, Ishwor Poudyal

Theses and Dissertations

X-ray free-electron lasers (XFELs) open the possibility of obtaining diffraction information from a single biological macromolecule. This is because XFELs can generate extremely intense X-ray pulses which are so short that diffraction data can be collected before the sample is destroyed. By collecting a sufficient number of single-particle diffraction patterns from many tilts of a molecule relative to the X-ray beam, the three-dimensional electron density can be reconstructed ab-initio. The resolution and therefore the information content of the data will ultimately depend largely on the number of patterns collected at the experiment. We estimate the number of diffraction patterns required …

Lattice And Charge Order In Layered Bi-Based Topological Insulators, Yanan Li

Theses and Dissertations

Bi2X3 (X=Se/Te) is a topological insulator, as well as a layered dichalcogenide. The topological properties of Bi2Se3 have gained a lot of interest over the past decade. However, as a layered chalcogenide, much of its uniqueness has not been fully discovered, e.g. hosting Charge Density Wave as reported in most other chalcogenides. With intercalation of Nb, Cu and Sr, Bi2Se3 becomes an unconventional superconductor. Together with its topological properties, A-Bi2X3 (A=Nb, Cu and Sr) have been proposed to be potential Topological superconductors. However, the mechanism of the unconventional SC in these compounds is still under discussion.

For my PhD research, …

Effects Of Intercalation And Deintercalation In Layered Materials: From Topological Insulators To Battery Cathodes, Uma Garg

Theses and Dissertations

Topological insulators are quantum materials which have insulating bulk and conducting surface. The surface states in these materials is protected by time reversal symmetry and spin-orbit coupling. The fascinating quantum properties of these materials could lead to high speed electronics and quantum computing. To explore the transport properties of these systems, I synthesized single crystals of SnTe and Sb2Se3 which are potential topological insulators. SnTe is a topological crystalline insulator in which topological surface states are protected by time reversal symmetry and crystal symmetry, in particular mirror symmetry. My Shubnikov-de Haas (SdH) oscillation study on the (001) surface of SnTe …

Characterization Of Fiber Bragg Grating Based, Geometry-Dependent, Magnetostrictive Composite Sensors, Edward Lynch

Theses and Dissertations

Optical sensors based on geometry dependent magnetostrictive composite, having potential applications in current sensing and magnetic field sensing are modeled and evaluated experimentally with an emphasis on their thermal immunity from thermal disturbances. Two sensor geometries composed of a fiber Bragg grating (FBG) embedded in a shaped Terfenol-D/epoxy composite material, which were previously prototyped and tested for magnetic field response, were investigated. When sensing magnetic fields or currents, the primary function of the magnetostrictive composite geometry is to modulate the magnetic flux such that a magnetostrictive strain gradient is induced on the embedded FBG. Simulations and thermal experiments reveal the …

Nuclear Magnetic Resonance Under Extreme Conditions, Anand Prashant Dwivedi

Theses and Dissertations

Nuclear Magnetic Resonance (NMR) is a prime characterization tool used to understand the structures and interactions in organic molecules, crystals, as well as non-crystalline materials. However, until now, the combination of NMR with high-pressure instrumentation such as Diamond Anvil Cells (DAC) was deemed unfeasible due to the high spatial and electrical costs of standard NMR electromagnets or the regular refill of cryogenic liquids for superconducting magnets. Standard NMR techniques also raises technical difficulties when combining high-pressure instrumentation with high-temperature techniques such as laser heating. In the first part of this thesis, we present the development of a low-cost and space-saving …