"Observation of broken time-reversal symmetry in the heavy-fermion superconductor UPt3"

E. R. Schemm: W. J. Gannon, C. M. Wishne, W. P. Halperin, and A. Kapitulnik; Science, 07/11/14.

Additional Authors: W. J. Gannon, C. M. Wishne, W. P. Halperin, and A. Kapitulnik

Abstract:

Models of superconductivity in unconventional materials can be experimentally differentiated by the predictions they make for the symmetries of the superconducting order parameter. In the case of the heavy-fermion superconductor UPt3, a key question is whether its multiple superconducting phases preserve or break time-reversal symmetry (TRS). We tested for asymmetry in the phase shift between left and right circularly polarized light reflected from a single crystal of UPt3 at normal incidence and found that this so-called polar Kerr effect appears only below the lower of the two zero-field superconducting transition temperatures. Our results provide evidence for broken TRS in the low-temperature superconducting phase of UPt3, implying a complex two-component order parameter for superconductivity in this system.