## CMT88

##
Thermal Conductivity of the Accidental Degeneracy and Enlarged Symmetry Group
Models for Superconducting UPt_{3}

**Author(s):** M.J. Graf, S.-K. Yip and J. A. Sauls

**Comments:** 18 pages with 7 figures

**Journal:**
Journal of Low Temperature Physics, 114, 257-273 (1999)
[DOI]
[PDF]
**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 UPt_{3}. 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 **c** 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,
κ_{c}/κ_{b},
provides a strong constraint of 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 UPt_{3}.
The models for the order parameter that fit the experimental data for the
**c** and **b** directions of the heat current are the *2D* E_{1g}
and E_{2u} models, for which the order parameters possess line
nodes in the **ab**-plane and point nodes along the **c** axis, and
the A_{1g}**+**E_{1g} model of Zhitomirsky and Ueda.
This model spontaneously breaks rotational symmetry in the **ab**-plane
below T_{c2} and predicts a large anisotropy for the **ab**-plane
heat current.

Paper:
[PDF]
[arXiv]