Physics Colloquium, April 21, 2009
The Search for Complex Order Parameter Symmetry in Unconventional Superconductors Dale J. Van Harlingen

University of Illinois at Urbana-Champaign

The discovery of the high-temperature superconductors in the 1980's revealed the existence of materials with unconventional pairing symmetry characterized by anisotropies in the magnitude and/or phase of the order parameter, in sharp contrast to conventional BCS superconductors. In this talk, I will describe the technique of Josephson interferometry and review how it was implemented to verify that the high temperature cuprates had a dx2-y2 pairing symmetry and how it can be applied to test the symmetry of more exotic superconducting phases. I will then describe our ongoing quest to identify superconductors with complex order parameters that exhibit broken time-reversal symmetry, focusing on the ruthenate superconductor Sr2RuO4 which is suspected to exhibit a chiral p-wave order parameter of the form px±ipy, and on the heavy fermion superconductor UPt3 which exhibits two distinct superconducting phases, one also suspected to be complex. In addition to exhibiting exciting new physics, complex superconductors have potential applications for topologically-protected quantum computing.

Dr. Van Harlingen's Web Site

4:00 p.m., Physics Research Building (PRB), Room 1080

Reception at 3:45 p.m., Atrium, PRB