Proximity induced superconductivity in Weyl semi-metals

TL;DR

This paper investigates how superconductivity can be induced in Weyl semi-metals through proximity effects, revealing confined coherence peaks near the interface and persistent Weyl nodes without a full bulk gap.

Contribution

It introduces a Green's function approach to study proximity-induced superconductivity in Weyl semi-metals, highlighting the localized nature of coherence peaks and the behavior of induced pairing amplitudes.

Findings

Coherence peaks are confined near the interface, not extending deep into the bulk.

Weyl nodes remain unaffected, no true bulk gap forms.

Induced pairing amplitudes decay exponentially into the bulk.

Abstract

We introduce superconducting proximity effects in Weyl semi-metals (WSM) with broken time reversal symmetry by tunnel coupling one of its surfaces to an s-wave superconductor using the Green's function approach. We find that the band structure develops coherence peaks, but despite the presence of metallic states in the bulk, the coherence peaks do not extend far into the bulk and remain confined to a few layers close to the interface, similar to the proximity effect in the topological insulators (TI) which are gapped in the bulk. The Weyl nodes remain unaffected, and in that sense, no true gap develops. We also study the various induced p and s-wave pairing amplitudes classified by their symmetries, as a function of the various relevant parameters of the theory and note the exponential decay of the induced pairings in the bulk both in the TI and the WSM, even at finite chemical potential.