Thermal Conductivity and Gap Structure of the Superconducting Phases of UPt3

TL;DR

This study provides detailed low-temperature thermal conductivity measurements of UPt3 across its superconducting phases, revealing unexpected magnetic field behavior and changes linked to order parameter symmetry transitions.

Contribution

It offers new experimental data on UPt3's thermal conductivity at very low temperatures and magnetic fields, testing theoretical predictions and exploring phase transition effects.

Findings

Thermal conductivity dominated by impurity states at lowest temperatures.

Unexpected magnetic field dependence of thermal conductivity.

Discontinuity in dκ/dT at Tc linked to phase transition.

Abstract

We present new measurements of the thermal conductivity of UPt3 down to very low temperatures (16mK) and under magnetic fields (up to 4 T) which cover all the superconducting phases of UPt3. The measurements in zero field are compared with recent theoretical predictions for the thermal conductivity, which is dominated by impurity states at the lowest temperatures studied. The measurements under magnetic field at low temperatures are surprising since they don't show the expected low field square root dependence. The discontinuity of d kappa/dT at Tc changes drastically when passing from the high field low temperature C phase to the low field high temperature A phase : this is related to the change of the symmetry of the superconducting order parameter when crossing the A - C phase transition.