Monday, September 29, 2014

Seminar: "A Taxonomy of the Magneto-Optical Responses of Cyclic Plasmon-Supporting Metal Oligomers" by David J. Masiello 11.6.14/ 11:00am-12:00pm/ CREOL 103

Seminar: "A Taxonomy of the Magneto-Optical Responses of Cyclic Plasmon-Supporting Metal Oligomers" by David J. Masiello
Thursday, November 6, 2014 11:00 AM to 12:00 PM
CREOL Room 103

David J. Masiello, Assistant Professor
Department of Chemistry, University of Washington

The optical-frequency magnetic and electric properties of cyclic plasmon-supporting metal nanoparticle oligomers are explored through a combination of scanning transmission electron microscopy (STEM)/electron energy-loss spectroscopy (EELS) simulation and first-principles theory. A tight-binding type model is introduced to explore the rich hybridization physics in these plasmonic systems and tested with full-wave numerical electrodynamics simulations of the STEM electron probe. Building from a microscopic electric model, connection is made at the macroscopic level between the hybridization of localized magnetic moments into delocalized magnetic plasmons of controllable magnetic order and the mixing of atomic p_z orbitals into delocalized pi molecular orbitals of varying nodal structure spanning the molecule. It is found that the STEM electrons are uniquely capable of exciting all of the different hybridized eigenmodes of the nanoparticle assembly---including multipolar closed-loop ferromagnetic and antiferromagnetic plasmons, giant electric dipole resonances, and radial breathing modes---by raster scanning the beam to the appropriate position. Comparison to plane-wave light scattering and cathodoluminescence (CL) spectroscopy is made. The presented work provides a unified understanding of the complete plasmon eigenstructure of such oligomer systems as well as of the excitation conditions necessary to probe each mode.

David J. Masiello completed a B.S. degree in mathematics from the University of Florida in 1999.  He then joined the University of Florida's Quantum Theory Project as a graduate student in chemical physics, where, in 2004, he received the Ph.D. degree working under the tutelage of Professor Yngve Öhrn.  His dissertation work explored a nonperturbative treatment of the interaction between molecules and the electromagnetic field, accounting for the redistribution of energy not only between different internal molecular degrees of freedom but also for its liberation to the dynamical electromagnetic field.  He then took two postdoctoral positions, one with Prof. William P. Reinhardt at the University of Washington (2004-2006) and the second with Professor George C. Schatz at Northwestern University (2006-2009).  Subsequently, David was hired back to the University of Washington in 2010 where he is now an assistant professor in theoretical chemistry.  Currently, Professor Masiello's research focuses on the theoretical understanding of a variety of nanoscale light-matter interactions involving the excitation of surface plasmon resonances.  Examples include electron energy-loss spectroscopy, cathodoluminescence, thermo-plasmonics, plasmon-enhanced catalysis, and plasmon-enhanced linear and nonlinear molecular optical phenomena.  As of Spring 2014, David is also a faculty member by courtesy in the Physics and Applied Mathematics departments at UW.

For more information:
Dr. Leonid Glebov


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