Bulletin of the American Physical Society
2014 Annual Fall Meeting of the APS Prairie Section
Volume 59, Number 19
Friday–Saturday, November 21–22, 2014; Monmouth, Illinois
Session C1: Poster Session |
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Room: Mellinger Commons |
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C1.00001: Gutzwiller Variational Method Mohammad Mahdi Valizadeh, Jamshid Moradi Kurdestany, Sashi Satpathy Finding the ground-state energy and many-body properties of strongly correlated systems, such as Mott insulators and high temperature superconductors, is currently a very important part of theoretical physics. In these materials, electron-electron correlations play a leading role in determining the phase diagram and other interesting physical properties. One of the most important model Hamiltonian methods to study these strongly-correlated systems is the Hubbard model. We use the Gutzwiller variational method, a well-known technique to find ground-state energy of correlated systems, to solve the one dimensional Hubbard model. In this problem, the Hamiltonian contains the kinetic energy of electrons from simple tight-binding method, and onsite Coulomb interaction between two electrons occupying the same lattice site. We compare the results of Gutzwiller variational method for the ground-state energy of the system with two other methods, Hartree approximation and Exact-Diagonalization. [Preview Abstract] |
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C1.00002: Multi-orbital physics and off-site interactions effects on phase diagram and shell structure in BH models Jamshid Moradi Kurdestany, Mohammad Mahdi Valizadeh We include two effects beyond the commonly applied Bose-Hubbard models, namely multi-orbital physics and off-site interactions. Both corrections turn out to be of crucial importance for a wide range of parameters. We use an inhomogeneous mean-field theory for three types of Bose-Hubbard (BH) models: (1) Extended Bose-Hubbard model (EBH) for spinless interacting bosons of one species; (2) two-species generalization of the spinless BH model; and (3) single-species, spin-1 BH model and extend it to include multi-orbital and density-induced tunneling in each case. In particular, we show how these change the phase diagram and shell structure in BH models. [Preview Abstract] |
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C1.00003: Observation of interlayer phonon mode in monolayer MoS2/WSe2 heterostructures Zhipeng Ye, Chao Ji, Casie Means-Shively, Heidi Anderson, Tim Kidd, Chun Hung Lui, Trond I. Andersen, Kuan-Chang Chiu, Cheng-Tse Chou, Jenn-Ming Wu, Yi-Hsien Lee, Rui He Transition metal dichalcogenides (TMDs), e.g. MoS2, MoSe2, WS2, and WSe2, have risen as a new generation of materials with remarkable properties. We have observed, by means of Raman spectroscopy, the formation of interlayer breathing mode phonons in heterobilayers formed from monolayers of MoS2 and WSe2. The heterogeneous layer breathing mode has a resonant frequency between those of bilayer MoS2 and bilayer WSe2. Its Raman response correlates strongly with the suppression of photoluminescence arising from interlayer electron-hole separation. While the interlayer phonon mode is hardly affected by the lattice mismatch and relative orientation of the two monolayers, it is sensitive to the interlayer spacing and can only be generated in heterostructures with atomically close layer-layer contact. [Preview Abstract] |
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C1.00004: Stability Analysis of Compounds Using the Computational and Physical Mechanics Myungjin Lee, Richard Wu, Minji Chung The physical activities and chemical catalytic efficiency of proposed metal oxide compounds are modeled and explained based on the compounds' mechanical repulsive forces, electron structures, and bond strengths. The ultimate goal of the research is to actualize green energy, achieving better selectivity and physical stability of the desired product molecule. In order to model the electron properties of the compounds, the computational and numerical methods are used. To check the stability and convergence of the solutions,~computational steps(N) versus energy(kcal/mol) curves for each metal compounds are presented.~The theoretical structure of each feasible catalytic palladium compound has been studied in this project. Based on the predicted physical stability of each molecule, the compound that can be used most efficiently to catalyze the reaction for the green energy can be determined. [Preview Abstract] |
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C1.00005: High frequency magnetic properties of patterned FeCoSiB multilayer thin films on silicon substrate W.B. Zhu, L. Zhang, H.Y. Zheng, X. Wang, M. Li, M. Bi, J.L. Xie, L.J. Deng Soft magnetic thin film with high saturation magnetization and high permeability, has been intensively studied in the several decades. In recent years, many research efforts have been placed on the controlling of resonance frequency (f$_{\mathrm{r}})$. One of the useful ways to tuning the resonance frequency (f$_{\mathrm{r}})$ is by patterning the magnetic thin film into periodic structure. In this article, FeCoSiB (patterned)/SiO$_{2}$/FeCoSiB multilayer was fabricated with the bottom layer patterned into periodical strip. In frequency-dependent permeability spectra measurement, f$_{\mathrm{r}}$ was increased with the increase of bottom layer thickness (T$_{1}$, range from 50nm to 250nm) and the full width at half maximum (FWHM) reached the maximum value of 2.7GHZ at T$_{1} =$ 50nm. Two resonance peaks of complex permeability spectrum were observed when T$_{1} =$ 100nm. In this bottom layer thickness, further changing upper layer thickness (T$_{2}$, range from 100nm to 300nm) haven't changed so much to the main peak position. We believed that the difference of anisotropy for different magnetic layers contribute to the coexistence of double resonance. [Preview Abstract] |
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C1.00006: Computational and Physical Analysis on Biomedical Imaging Using Alternative Method for Higher Resolution Richard Wu, Kyuyeol Kim, Sewon Park An MRI (magnetic resonance imaging) scan is a technique that uses magnetism, computers, and radio waves to produce images of the intended subject.~This is a common medical imaging technique used to determine the anatomy and physiology of the subject in multiple areas. The technique is widely in use for medical diagnosis, disease, staging of diseases and subject studies etc.~To get the image from MRI, frequency has to be transferred to image using mathematical and computational transformations.~Since the~Low spatial frequencies contain the most of the information about the image, not all of the data is necessary in producing the required image. A proper function can be multiplied by original k-space to get reduced size of frequencies which will be used to determine output images. In this research, new computational MRI physics experiments were carried out with several modified filters to reduce the ringing effect, to improve the resolution of an MRI image to a degree, and to propose an efficient function as a new filter. [Preview Abstract] |
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C1.00007: Improving Capacitances and Supercapacitors with Metal-Organic Frameworks Jae June Lee, Kyuyeol Kim, Richard Kyung If the space between the plates of a capacitor is filled with an insulator, the capacitance of the capacitor will be improved. A supercapacitor can hold hundreds of times more electrical density than a standard capacitor. In this research, we considered two cases of capacitors to improve capacitances in the electric device. First, considering the effective capacitance of a capacitor filled with multiple slabs of dielectrics with different dielectric constants, we showed the influence of the multiple dielectric slabs~inserted in one capacitor on the electric field distribution in the capacitor system. Also changing energy stored in the capacitor is observed when the dielectric slab is withdrawn from the capacitor. And second, this study shows how metal-organic frameworks (MOFs) in the supercapacitors can be incorporated into electrical devices to generate high capacitance; in particular, a MOF with a transitional metal exhibits exceptionally high capacitance and charge/discharge cycles. [Preview Abstract] |
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C1.00008: Optical Exploration of Cellular Microenvironments Joshua Weber, Kevin Eliceiri Cell function and behavior are influenced by various local factors. The cellular microenvironment includes surrounding cells and the extracellular matrix, molecules and proteins that provide structural and functional support. In addition to the local chemistry, the physical properties of these environs affect cell behavior, as do the mechanical forces they exert. At the Laboratory for Optical and Computational Instrumentation, we use multiple optical imaging modalities to explore cellular microenvironments. A principle tool is multiphoton fluorescent excitation microscopy. Based on non-linear effects, this technique reduces scatter and allows for deeper optical exploration. This is particularly useful in 3D tissue imaging, as it permits optical sectioning of intact tissues. Fluorescence lifetime microscopy reveals environmental effects through variations in the delay between excitation and decay. With spectral discrimination, multiple fluorophores, and thus multiple aspects of the environment, can be examined concurrently. We also experiment with high-speed time-of-flight techniques based on indirect scattering, which permit imaging of otherwise inaccessible regions. With these imaging modalities, we explore cellular microenvironments in a range of biological samples. [Preview Abstract] |
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