Categories: Physics - Condensed Matter (PHYS-CM)
Speaker: Joseph W. Brill, U. of Kentucky
Date & Time: October 12, 2012 - 1:30pm
Location: Serin Physics 385E
We use changes in infrared properties to study the presence of quasiparticles (i.e. “band” electrons) in systems in which the diffusion of charge takes times longer than ~ 10 ms. In particular, we study changes in the local density of quasiparticles, which absorb IR light, caused by application of voltage to electrodes on or near the sample. For charge-density-wave (CDW) conductors, the CDW is deformed (i.e. polarized) by application of voltage across the sample and quasiparticles act to screen the deformation. Measurements of the frequency dependence of the electro-optic response give information on the dynamics of CDW polarization, including the CDW diffusion constant. For thin-film organic field-effect transistors, carriers (typically holes) are pulled onto the interface between the semiconductor and dielectric by application of a gate voltage. Measurements of the frequency dependence of the electro-optic response can be used to test models of how the FET charges/discharges and, in the simplest case, to determine the mobility of the holes.
Host: Vitaly Podzorov