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   COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS        
                   School of Computational Sciences     
                           (CSI 898-Sec 001) 
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  Quantum Mirages in Scanning Tunneling Microscopy of Nanostructures: 
  the complimentary roles of analytic models and computer simulations

                             J. W. Gadzuk
    National Institute of Standards and Technology, Gaithersburg, MD

    Almost everyone has seen Eigler's stunning STM pictures in which 
individual atoms were assembled to form a chosen two-dimensional 
configuration, call it a nanostructure, on a metal substrate.  Some 
of these shapes, when closed, have been referred to as quantum corrals.  
A particularly intriguing example is an elliptical corral (major axis 
<15 nm) composed of up to 70 individually-placed atoms or molecules 
on a Cu(111) surface.  It has been observed with the STM that both the 
pictorial image and the spectroscopic signature of a single atom such 
as Co placed at one of the foci showed a (corral-size-dependent) mirage 
when STM measurements were made at the opposing unoccupied focus.  The 
physics of these quantum mirages will be discussed. This is a nice example 
of a timely problem in high-visibility contemporary science and technology 
which can usefully be addressed by both analytic theory and 
computationally-more-intensive modeling, as will be demonstrated.

                         Monday , September 29, 2003
                                  4:30 pm
                        Room 206, Science & Tech. I

Refreshments will be served at 4:15 PM.
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Find the schedule at http://www.scs.gmu.edu/lcdm/seminar/schedule.html