This note is to let y'all know my Ph.D. defense is scheduled for next
week, and to invite those in the area to attend the public session.

It will be at 3:15 PM, April 15. It will be in Ginzton Lab 299, the
upstairs conference room.

If you know you might come, please drop me a note so that I can make sure
we have enough chairs, etc..

Take care,

Bill

Here's the abstract:

This work uses photothermal microscopy to measure temperature-dependent
changes in differential optical reflectivity (DOR) as a function of sample
temperature.  All measurements were made on samples of untwinned
YBa2Cu3O7-x (YBCO), a high-temperature superconductor.  Photothermal
microscopy is a pump-probe thermal modulation technique using two focused
laser beams to generate and detect thermal waves on a sample. 

We will present measurements made at five probe frequencies in the range
of 0.8-1.96 eV. Although the probe energy is at least 20 times the
expected superconductivity energy gap in YBCO, we have found distinctive
evidence of the superconducting transition at all frequencies. 
Microscopic spatial resolution and polarization control permit the
characterization of small (~20 um) uniform YBCO regions in both the a and
b directions.  The observed DOR frequency variation is inconsistent with
simple models.  We believe this frequency variation is evidence of new
physical processes in YBCO. To date, no theory of high-temperature
superconductivity has successfully treated this frequency variation.