Weyl superconductor phases in a Weyl-semimetal/superconductor multilayer

TL;DR

This paper investigates how multilayer structures of Weyl semimetals and superconductors induce topologically nontrivial superconducting phases, revealing the emergence and manipulation of Majorana nodes and topological phases through the proximity effect.

Contribution

It introduces a theoretical model using the Kronig-Penney approach to analyze the proximity effect in Weyl-semimetal/superconductor multilayers, highlighting the control of Majorana nodes and topological phases.

Findings

Decoupling of Weyl nodes into Majorana fermions due to proximity effect

Fermi velocity mismatch and interface barriers can gap out Majorana nodes

Transition from Weyl-superconductor to topological-superconductor phases with odd Chern numbers

Abstract

Topologically nontrivial superconducting phases have been engineered in topological materials by the proximity effect in contact with conventional superconductors. In this paper, by using the method of the Kronig-Penney model, we study the superconducting proximity effect in the bulk electronic states of Weyl semimetals by considering a multilayer structure consisting of Weyl-semimetal and superconductor layers. Due to the proximity effect, two Weyl nodes are decoupled into four nodes of Majorana fermions resulting in Weyl-superconductor phases or three-dimensional extension of topological-superconductor phases. We find that mismatch of the Fermi velocity and potential barriers at the interface gap out Majorana nodes, thus turn Weyl-superconductor phases with four Majorana nodes into Weyl-superconductor phases with half of Majorana nodes and topological-superconductor phases with odd integer Chern numbers.