Thermal Conductivity of the Accidental Degeneracy and Enlarged Symmetry Group Models for Superconducting UPt3 |
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Authors: | M. J. Graf S.-K. Yip J. A. Sauls |
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Affiliation: | (1) Department of Physics & Astronomy, Northwestern University, Evanston, Illinois 60208-3112, USA;(2) Center for Materials Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA |
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Abstract: | We present theoretical calculations of the thermal conductivity for the accidental degeneracy and enlarged symmetry group models that have been proposed to explain the phase diagram of UPt3. The order parameters for these models possess point nodes or cross nodes, reflecting the broken symmetries of the ground state. These broken symmetries lead to robust predictions for the ratio of the low-temperature thermal conductivity for heat flow along the axis and in the basal plane. The anisotropy of the heat current response at low temperatures is determined by the phase space for scattering by impurities. The measured anisotropy ratio, c/b, provides a strong constraint on theoretical models for the ground state order parameter. The accidental degeneracy and enlarged symmetry group models based on no spin-orbit coupling do not account for the thermal conductivity of UPt3. The models for the order parameter that fit the experimental data for the and directions of the heat current are the 2D E1gand E2umodels, for which the order parameters possess line nodes in the ab-plane and point nodes along the axis, and the A1gE1gmodel of Zhitomirsky and Ueda. This model spontaneously breaks rotational symmetry in the ab-plane below Tc2and predicts a large anisotropy for the ab-plane heat current. |
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