Superconductivity, Glue, and the Pseudogap
|Date/Time:||Monday, 03 Feb 2014 from 4:10 pm to 5:00 pm|
Superconductivity is an "emergent" phenomenon. What that buzz word means here is that superconductivity-old style and likely new-requires theoretical insight outside the scope of the theory of metals at the time understanding emerged. Completely new ideas were needed-then by Bardeen, Cooper, and Schreiffer (BCS) -and now we wait for the insight while diligently making measurements so good and effective that we know the problem has to yield eventually. But we're not there yet. What is essential is to find the analog of the "phonon" glue that BCS discovered was the way to make electrons in a metal quantum condense into a superconductor. The glue has to have some sort of dynamic response, and has to be ubiquitous. We review here some aspects of superconductivity, lay out incompletely and with bias some of the problems before us in the grand challenge to understand high temperature superconductivity, and describe our recent measurements using Resonant Ultrasound Spectroscopy that reveal a "pseudogap" and hint at some forward progress*.
*Bounding the pseudogap with a line of phase transitions in YBa2Cu3O6+?, Arkady Shekhter, B. J. Ramshaw, Ruixing Liang, W. N. Hardy, D. A. Bonn, Fedor F. Balakirev, Ross D. McDonald, Jon B. Betts, Scott C. Riggs & Albert Migliori, Nature 498, 75-77 (06 June 2013)