1,480 research outputs found
Strong-coupling electron-phonon superconductivity in noncentrosymmetric quasi-one-dimensional KCrAs
I study the lattice dynamics and electron-phonon coupling in
non-centrosymmetric quasi-one-dimensional KCrAs using density
functional theory based first principles calculations. The phonon dispersions
show stable phonons without any soft-mode behavior. They also exhibit features
that point to a strong interaction of K atoms with the lattice. I find that the
calculated Eliashberg spectral function shows a large enhancement around 50
cm. The phonon modes that show large coupling involve in-plane motions
of all three species of atoms. The dependent electron-phonon
coupling decreases strongly away from the plane. The total
electron-phonon coupling is large with a value of , which readily explains the experimentally observed large mass
enhancement
Proposal for ultrafast switching of ferroelectrics using mid-infrared pulses
I propose a method for ultrafast switching of ferroelectric polarization
using mid-infrared pulses. This involves selectively exciting the highest
frequency phonon mode of a ferroelectric material with an intense
mid-infrared pulse. Large amplitude oscillations of this mode provides a
unidirectional force to the lattice such that it displaces along the lowest
frequency phonon mode coordinate because of a nonlinear coupling of the
type between the two modes. First
principles calculations show that this coupling is large in transition-metal
oxide ferroelectrics, and the sign of the coupling is such that the lattice
displaces in the switching direction. Furthermore, I find that the lowest
frequency mode has a large order anharmonicity, which
causes a discontinuous switch of electric polarization as the pump amplitude is
continuously increased
University of Alaska Southeast Report on Institutional and Programmatic Accreditation: Report to the UA Board of Regents - September 2014
Research, Creative Works, and Commercialization at UAA FY15 through FY16 YTD.
The UAA Research and Commercialization trend is upward. UAA is experiencing significant growth in research, creative works, and commercialization. We are pursuing a strategic approach to fostering, supporting, and expanding faculty and student research efforts and commercialization by creating a climate of innovation and collaboration
A Prospectus on Substantive Change
Prepared for The Commission on Colleges, Northwest Association of Schools and Colleges, October 1, 1987. For consideration by the Commission on Colleges at its December 5 and 6, 1987, meeting at the Salt Lake Hilton Hotel
Sex Offender Treatment Program: Preliminary Description
This report provides a summary of the history of sex offender treatment in Alaska, including the current status of treatment programs offered by the Alaska Department of Corrections, a review of literature on sex offender treatment and recidivism issues, and a summary of the descriptive characteristics of individuals who came in contact with the Hiland Mountain Correctional Center from January 1987 to March 1993.Alaska Department of CorrectionsIntroduction / Sex Offender Treatment in Alaska / Literature Review / Methodology / Results / Conclusion and Recommendations / Bibliograph
Interplay between structure and chemistry of materials and their physical properties
First principles calculations provide a powerful tool for sorting out the interplay of chemical composition and structure with the physical properties of materials. In this dissertation, I discuss the physical properties and their microscopic basis within this framework for following illustrative examples. (i) The Zintl phase hydrides, where I find H is anionic and the formation of covalent sp2 bonds in the Al/Ga/Al-Si planes, which is a highly unusual bonding configuration for these elements. (ii) PbTe, which shows strong coupling between the longitudinal acoustic and transverse optic modes that may explain its low thermal conductivity. (iii) The double perovskites BiPbZnNbO6 and BiSrZnNbO6, where introducing size disorder at A-site prevents the BO6 octahedra from tiling and enhances the polar behavior. (iv) FeSe, which shares the salient electronic and magnetic features of other Fe superconductors and cannot be described as a conventional electron phonon superconductor. (v) NbFe2, which is near a magnetic quantum critical point and shows strong competition between various magnetic orderings that may explain its unusual non-Fermi liquid behavior at very low temperatures. (vi) The nickel analogues of Fe superconductors LaNiPO and BaNi2As2, where I show that superconductivity is of conventional electron-phonon type in contrast to the Fe-based superconductors. (vii) Noncentrosymmetric LaNiC2, which I find is a conventional electron-phonon superconductor with intermediate coupling
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