Speaker: Aharon Kapitulnik, Stanford University
Date & Time: December 4, 2007 - 1:30pm
Location: Serin E385
Search for Broken Time Reversal Symmetry States in Unconventional Superconductors
Physics and Astronomy
Aharon Kapitulnik, Stanford University
1:30, Serin E385
The Polar Kerr Effect (PKE) is sensitive to time-reversal symmetry breaking (TRSB) since it measures the existence of an antisymmetric contribution to the real and imaginary parts of the frequency-dependent dielectric sensor, and such a contribution is necessarily absent if TRS is not broken in the material. In order to measure the very small static TRSB effect in superconductors, we have developed a new PKE technique based on a fiber Sagnac interferometer with a zero-area Sagnac loop. Initially the technique has been used to discover TRSB in Sr2RuO4, thus strongly suggesting a p+ip symmetry for its order parameter. In the talk I will describe the technique and the detailed studies on Sr2RuO4 as well as subsequent studies of high-Tc superconductors and selected heavy fermion materials. In particular I will show PKE results on high quality YBa2Cu3O6+x shedding new light on the origin of the pseudogap in this system.