"Quantum Femtosecond Magnetism"

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Date/Time:Monday, 29 Apr 2013 from 4:10 pm to 5:00 pm
Location:Physics 0005
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Dr. Jigang Wang (Iowa State University)

The technological demand to push the gigahertz switching speed limit of today's magnetic memory and logic devices into the terahertz regime underlies the entire field of spin-electronics and integrated multi-functional devices. This challenge is explored by a new paradigm called quantum femtosecond magnetism--magnetic phase transitions driven by quantum spin flucations and by femtosecond-laser-excited inter-atomic coherences/entanglement. By analogy to femtosecond chemistry and photosynthetic dynamics--in which photoproducts of chemical/biochemical reactions can be influenced by creating suitable superpositions of molecular states-laser-driven inter-atomic coherent couplings can dynamically generate transient magnetic correlations and, thereby, switch magnetic order by 'suddenly' breaking the delicate balance between competing phases of strongly correlated electronic materials. In this talk, I discuss our observation of the quantum femtosecond magnetism in one colossal magneto-resistive manganite material. The discovery is important for establishing the framework to seek the fundamental magnetic switch speed limit and for understanding what initiates the magnetic nonlinear dynamics during the very early unadiabatic timescales, which set the "initial condition" of subsequent time evolution dictated by the free energy and excited potential surface.
Brief bio for Jigang Wang
Since 2008, he is an assistant professor in the Department of Physics and Astronomy at Iowa State University and associate staff scientist in Ames laboratory of US department of Energy. He received his Ph.D. from Rice University at 2005 with Jun Kono and joined Lawrence Berkeley National Laboratory as postdoc under Daniel Chemla. He is working in experimental condensed matter physics, focusing on femtosecond laser spectroscopy and many-body correlation phenomena in nanostructures and quantum materials. His current projects include ultrafast magnetism in strongly correlated electrons, dynamics of iron pnictide superconductors, nonlinear optics in metamaterials, low dimensional quantum physics in carbon nanotubes and graphenes. He is recipient of the NSF early CAREER award and LAS Award for Early Achievement in Research at Iowa State University.