Abstract
The polar Kerr effect in the high- superconductor was measured at zero magnetic field with high precision using a cyogenic Sagnac fiber interferometer. We observed nonzero Kerr rotations of order appearing near the pseudogap temperature and marking what appears to be a true phase transition. Anomalous magnetic behavior in magnetic-field training of the effect suggests that time reversal symmetry is already broken above room temperature.
- Received 15 November 2007
DOI:https://doi.org/10.1103/PhysRevLett.100.127002
©2008 American Physical Society