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# Twofold Spontaneous Symmetry Breaking in the Heavy-Fermion Superconductor UPt3

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Department of Physics, Tokyo Institute of Technology, Meguro 152-8551, Japan.
(Impact Factor: 7.73). 04/2012; 108(15):157002. DOI: 10.1103/PhysRevLett.108.157002
Source: PubMed

ABSTRACT The field-orientation dependent thermal conductivity of the heavy-fermion superconductor UPt3 was measured down to very low temperatures and under magnetic fields throughout the distinct superconducting phases: B and C phases. In the C phase, a striking twofold oscillation of the thermal conductivity within the basal plane is resolved reflecting the superconducting gap structure with a line of node along the a axis. Moreover, we find an abrupt vanishing of the oscillation across a transition to the B phase, as a clear indication of a change of gap symmetries. We also identify extra two line nodes below and above the equator in both B and C phases. From these results together with the symmetry consideration, the gap function of UPt3 is determined as a E(1u) representation characterized by a combination of two line nodes at the tropics and point nodes at the poles.

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