Theory of tunneling spectroscopy in UPd2Al3

TL;DR

This paper analyzes tunneling spectroscopy in UPd2Al3 to determine its superconducting order parameter symmetry, ruling out some proposals and suggesting experiments to distinguish remaining possibilities.

Contribution

It provides a theoretical analysis that excludes certain order parameter symmetries based on tunneling data and proposes an experiment to identify the correct symmetry.

Findings

Experimental results are inconsistent with sin(k3) and exp(iφ) sin(k3) symmetries.

Proposes a tunneling experiment to differentiate cos(k3) and cos(2k3) symmetries.

Clarifies the nature of the order parameter in UPd2Al3.

Abstract

There is still significant debate about the symmetry of the order parameter in the heavy-fermion superconductor UPd$_{2}$Al$_{3}$, with proposals for cos(k3), cos(2k3), sin(k3),and exp(i\phi) sin(k3). Here we analyze the tunneling spectroscopy of this compound and demonstrate that the experimental results by Jourdan et al are inconsistent with the last two order parameters, which are expected to show zero-bias conductance peaks. We propose a definitive tunneling experiment to distinguish between the first two order parameters.