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Full-Text Articles in Physical Sciences and Mathematics
Magnetic Order And Dimensional Crossover In Optical Lattices With Repulsive Interaction, Jie Xu
Magnetic Order And Dimensional Crossover In Optical Lattices With Repulsive Interaction, Jie Xu
Dissertations, Theses, and Masters Projects
One of the most interesting and challenging problems in physics is understanding strongly correlated many-body systems, where strong interactions can yield many remarkable phenomena such as superfluidity in 4He, high-temperature superconductivity, etc. In order to attack these problems, we often need to reduce the complexity of the systems to simple models in hopes of getting better insights into the properties of the systems. The Hubbard model, the focus of this dissertation, is one of the most famous examples of such model, which describes a tunneling of electrons between nearest neighbor sites of a lattice with on-site interactions. This simple model …
Advanced Topographic Characterization Of Variously Prepared Niobium Surfaces And Linkage To Rf Losses, Chen Xu
Dissertations, Theses, and Masters Projects
Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. The shallow penetration (∼ 40 nm) of the RF into superconducting niobium lends great importance to SRF cavity interior surface chemistry and topography. These in turn are strongly influenced by the chemical etching "surface clean-up" that follows fabrication.;The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions …