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semi-Dirac, semi-Weyl semi-Half Metals in Oxide Nanostructures

Warren E. Picket (UCDavis, USA)
Tue, 17/07/2012 - 12:00pm to 1:00pm
S13-M01-11 (Physics Conference Room)
Event Type: 


The subjects of graphene science, oxide nanostructures, and the topological nature of materials comprise three of the most active topics in materials physics at this time.  After working on oxide polar interfaces (LAO/STO) for some time, we asked whether non-polar interfaces between oxides held the possibility for surprises.  Studying VO2/TiO2 multilayers, we discovered computationally a new type of 2D point 'Fermi surface' system: linear (Weyl) dispersion in one direction, quadratic (Dirac) dispersion in the perpendicular direction.  Such a system, which we dubbed semi-Dirac for simplicity, lies midway between graphene and conventional zero-gap semiconductors in many respects.  Unlike both, however, it displays extreme anisotropy in its electronic structure and and low-energy propeties. Alas, unlike the poit of essence in graphene, this point is non-topological.  Our studies will be reviewed in this talk.

Speaker's bio:

Warren Pickett obtained his B.S. (Physics, Math) and M.S. (Physics) degrees at Wichita State University before going to SUNY-Stony Brook, New York to complete his PhD in theoretical condensed matter physics in 1975. He had postdoctoral research appointments at the University of Bristol, England, at UC Berkeley, and at Northwestern University, where his research centered on the electronic structure of crystalline metals and semiconductors, on semiconductor interfaces, and on superconductivity. In 1979 he accepted a research scientist position at the Naval Research Laboratory in Washington DC. Early in his years at NRL, Warren increased his activity in large scale calculations of the properties of condensed phases, using the NRL ASC supercomputer and early Cray machines (Boeing) to carry out a study of, for example, the heavy fermion superconductor UBe13, which has 28 atoms in the unit cell.

He was elected Fellow of the American Physical Society in 1989, and shared 2nd Prize in the IBM Supercomputing Competition in 1990. At NRL Pickett was awarded the E. O. Hulburt Award in 1990 and the Sigma Xi Technical Achievement Award in Pure Science in 1993. He was appointed Senior Scientist at NRL in 1992. He received Alan Berman Research Publication Awards at NRL in 1983, 1998,1989, and 1992. In 1997 Warren took a professorship in physics at UC Davis, where he is a participant in an interdisciplinary program in nanophases as well as working in condensed matter physics research programs. Warren Pickett has served on the editorial board of the Journal of Superconductivity since its foundation in 1989, and on the editorial board of Chemical Design Automation News from 1993-1998. He was a member of the Council of the American Physical Society from 1996-1999. In 2001 he became Editor of the Journal of the Physics and Chemistry of Solids, published by Elsevier Press.

His research focusses on moving toward a first principles description of the properties of complex crystalline materials, and he has begun collaborations with solid state chemists and chemical engineers as well as solid state theorists and experimentalists. Recently his interest in materials has expanded to include magnetic materials that become superconducting, ferroelectric insulators that become ferromagnetic, and more generally novel magnetic and superconducting compounds that are of interest to both condensed matter physicists, solid state
chemists, and materials scientists. He has over 275 publications in the primary scientific literature, and has active collaborations in Europe, Asia, South America, and across the USA.


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