111 research outputs found
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FINAL REPORT DOE Grant: DE-FG02-89ER45391
The work reported here took place at the University of Minnesota from 07/01/1989 to 06/30/2006. Most of this work focused on computational materials applied to oxides during the first part of this funding period and to nanoscale materials toward the end of the funding period. This funding resulted in three monographs, 36 invited articles or book chapters, 160 articles in refereed journals and 89 invited talks. The funding helped train 13 PhD students and one masters student. The PI received two national research awards for this work. A list of these contributions are presented
FINAL REPORT: Scalable Methods for Electronic Excitations and Optical Responses of Nanostructures: Mathematics to Algorithms to Observables
Work in nanoscience has increased substantially in recent years owing to its potential technological applications and to fundamental scientific interest. A driving force for this activity is to capitalize on new phenomena that occurs at the nanoscale. For example, the physical confinement of electronic states, i.e., quantum confinement, can dramatically alter the electronic and optical properties of matter. A prime example of this occurs for the optical properties of nanoscale crystals such as those composed of elemental silicon. Silicon in the bulk state is optically inactive due to the small size of the optical gap, which can only be accessed by âindirectâ transitions. However, at the nanoscale, this material becomes optically active. The size of the optical gap is increased by confinement and the conservation of crystal momentum ceases to hold, resulting in the viability of indirect transitions. Our work associated with this grant has focused on developing new scalable algorithms for describing the electronic and optical properties of matter at the nanoscale such as nano structures of silicon and related semiconductor properties
Out-of-plane polarization and topological magnetic vortices in multiferroic CrPSe
Two-dimensional (2D) multiferroic materials are ideal systems for exploring
new coupling mechanisms between different ferroic orders and producing novel
quantum phenomena with potential applications. We employed first-principles
density functional theory calculations to discover intrinsic ferroelectric and
anti-ferroelectric phases of CrPSe, which show ferromagnetic order and
compete with the centrosymmetric phase with an antiferromagnetic order. Our
analysis show that the electrical dipoles of such type-I multiferroic phases
come from the out-of-plane displacements of phosphorus ions due to the
stereochemically active lone pairs. The coupling between polar and magnetic
orders creates the opportunity for tunning the magnetic ground state by
switching from the centrosymmetric to the ferroelectric phase using an
out-of-plane electric field. In ferroelectric and antiferroelectric phases, the
combination of easy-plane anisotropy and Dzyaloshinskii-Moriya interactions
(DMI) indicate they can host topological magnetic vortices like meron pairs.Comment: 7 pages, 3 figures, and the supplementary materia
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