Nodal gap detection through polar angle-resolved density of states measurements in uniaxial superconductors

Abstract

We propose a spectroscopic method to identify the nodal gap structure in unconventional superconductors. This method is best suited for locating the horizontal line node and for pinpointing the isolated point nodes by measuring polar angle (θ) resolved zero-energy density of states N(θ). This is measured by specific heat or thermal conductivity at low temperatures under a magnetic field. We examine a variety of uniaxially symmetric nodal structures, including point and/or line nodes with linear and quadratic dispersions, by solving the Eilenberger equation in vortex states. It is found that (a) the maxima of N(θ) continuously shift from the antinodal to the nodal direction (θn) as a field increases accompanying the oscillation pattern reversal at low and high fields. Furthermore, (b) local minima emerge next to θn on both sides, except for the case of the linear point node. These features are robust and detectable experimentally. Experimental results of N(θ) performed on several superconductors, UPd2Al3,URu2Si2,CuxBi2Se3, and UPt3, are examined and commented on in light of the present theory.

Source-reported materials — not catalogue approval

Similar papers