Electronic properties of the Weyl semimetals Co$_2$MnX (X=Si, Ge, Sn)

TL;DR

This study uses first-principles calculations to identify Weyl semimetal behavior in ferromagnetic Co$_2$MnX Heusler compounds, revealing complex topological features and potential for experimental observation.

Contribution

It demonstrates that Co$_2$MnX compounds are Weyl semimetals with unique topological band crossings protected by mirror symmetry.

Findings

Presence of non-trivial topological band crossings near the Fermi level.

Complex 3D geometries of band crossings with Hopf links and nodal lines.

Spin-orbit interaction splits nodal lines into Weyl points within the band gap.

Abstract

Using first-principles electronic structure calculations, we show that ferromagnetic Heusler compounds Co$_2$MnX (X= Si, Ge, Sn) present non-trivial topological characteristics and belong to the category of Weyl semimetals. These materials exhibit two topologically interesting band crossings near the Fermi level. These band crossings have complex 3D geometries in the Brillouin zone and are characterized by non-trivial topology as Hopf links and chain-like nodal lines, that are protected by the perpendicular mirror planes. The spin-orbit interaction split these nodal lines into several zero-dimensional Weyl band crossings. Unlike previously known topologically non-trivial Heusler materials, these majority-spin band crossings lie in the band gap of minority spin bands, potentially facilitating its experimental realization.