Condensed Matter Seminar

Strontium ruthenate Sr2RuO4 is an odd-parity superconductor, shown to exhibit p-wave pairing. Some of the possible p-wave states can further break time-reversal symmetry (TRS). However, unlike other known TRS breaking effects in solids, this case does not imply a "magnetic effect" since any such signal will be screened by the Meissner effect (except for surfaces, domain walls and imperfections). In the past two years, we have pursued a direct test of the broken time-reversal-symmetry in the bulk of Sr2RuO4 and other superconductors with potentially broken time reversal symmetry state, without relying on imperfections and defects by measuring the Polar Kerr effect (PKE). PKE is sensitive to TRS breaking since it measures the existence of an antisymmetric contribution to the real and imaginary parts of the frequency-dependent dielectric tensor, and such a contribution is necessarily absent if TRS is not broken in the material. In order to measure the very small static TRS-breaking effect in superconductors, we have developed a new PKE technique based on a fiber Sagnac interferometer with a zero-area Sagnac loop. Results on Sr2RuO4 as well as other unconventional superconductors will be shown.

1. Jing Xia, Maeno Yoshiteru, Peter T. Beyersdorf, M. M. Fejer,
Aharon Kapitulnik, Phys. Rev. Lett. 97 (2006),167002.