Physics & Astronomy Colloquium

3:30 PM, Friday, August 25, 2006

Room 155, Chem-Phys Building

Dr. Joe Brill

Department of Physics and Astronomy
University of Kentucky

``Electro-Optic Studies of the Dynamics of Charge-Density-Wave Polarization in Blue Bronze''

This year marks the 30th anniversary of the discovery of "sliding" charge-density-waves (CDW's), the first example of collective electron transport after superconductivity. Despite their long history, CDW's remain an area of active research because of the variety of unusual properties they exhibit and their analogies to phenomena in other materials. While it has long been known that in addition to sliding through the crystal, CDW's polarize (i.e. strain) in an applied voltage, measurements of the CDW polarization have proven illusive. For the last few years, our group has used a novel electro-optic effect to probe the dynamics of CDW polarization, in particular how quickly the polarization can change as functions of position and voltage. Our results indicate that the change in strain slowly propagates from the current contacts with a speed ~ V^1/2. Once it starts, the strain at each point relaxes very slowly, with a time constant ~ 1/V^3/2. Critical slowing down has not yet been observed at the depinning threshold; instead, the distribution of relaxation times broadens.

Refreshments will be served in CP 179 at 3:15 PM