Weyl point immersed in a continuous spectrum: an example from superconducting nanostructures

TL;DR

This paper explores how a Weyl point in a superconducting nanostructure behaves when connected to normal leads, revealing how topological features are smoothed and detectable through tunnel currents and charge density analysis.

Contribution

It introduces a model of a Weyl point immersed in a continuous spectrum, analyzing the effects of tunnel coupling and providing methods to detect topological properties.

Findings

Topological charge is distributed over a parameter space region.

Tunnel currents can be used to detect Weyl points.

Normal lead pumping aids in topological effect detection.

Abstract

A Weyl point in a superconducting nanostructure is a generic minimum model of a topological singularity at low energies. We connect the nanostructure to normal leads thereby immersing the topological singularity in the continuous spectrum of the electron states in the leads. This sets another simple and generic model useful to comprehend the modification of low-energy singularity in the presence of continuous spectrum. The tunnel coupling to the leads gives rise to new low energy scale $\Gamma$ at which all topological features are smoothed. We investigate superconducting and normal currents in the nanostructure at this scale. We show how the tunnel currents can be used for detection of the Weyl point. Importantly, we find that the topological charge is not concentrated in a point but rather is spread over the parameter space in the vicinity of the point. We introduce and compute the resulting topological charge density. We also reveal that the pumping to the normal leads helps to detect and investigate the topological effects in the vicinity of the point.