Weyl semimetals and superconductors designed in an orbital selective superlattice

TL;DR

This paper introduces design principles for creating 3D Weyl semimetals and superconductors using an orbital selective superlattice, enabling tunable Weyl nodes and potential Majorana states.

Contribution

It develops a generalized model and Hamiltonian framework for engineering Weyl nodes and superconducting states in layered superlattices with broken mirror symmetry.

Findings

Tunable Weyl nodes with linear dispersion can be engineered.

A helical Weyl band can be realized at the Fermi level in superconductors.

Implications for anomalous Hall effect and Majorana states are discussed.

Abstract

We propose two complementary design principles for engineering three-dimensional (3D) Weyl semimetals and superconductors in a layer-by-layer setup which includes even and odd parity orbitals in alternating layers - dubbed orbital selective superlattice. Such structure breaks mirror symmetry along the superlattice growth axis which, with the help of either a basal plane spin-orbit coupling or a spinless p+ip superconductivity, stabilizes a 3D Dirac node. To explore this idea, we develop a 3D generalization of Haldane model and a Bogoliubov-de-Gennes (BdG) Hamiltonian for the two cases, respectively, and show that a tunable single or multiple Weyl nodes with linear dispersion in all spatial directions can be engineered desirably in a widespread parameter space. We also demonstrate that a single helical Weyl band can be created at the $\Gamma$-point at the Fermi level in the superconducting case via gapping out either of the orbital state by violating its particle-hole symmetry but not any other symmetries. Finally, implications of our results for the realization of anomalous Hall effect and Majorana bound state are discussed.