Strain-induced topological charge control in multifold fermion systems

TL;DR

This paper demonstrates that applying strain to multifold fermion systems like CoSi can control their topological charge distribution, enabling the creation or destruction of multifold fermions and Weyl points, thus tuning their topological properties.

Contribution

It introduces a method to manipulate topological charges in multifold fermion systems through strain, supported by first-principles calculations and an effective low-energy model.

Findings

Strain can destroy multifold fermions in CoSi.

Strain can induce Weyl points by breaking rotational symmetry.

Strain engineering effectively tunes topological properties.

Abstract

Multifold fermion systems feature free fermionic excitations, which have no counterparts in high-energy physics, and exhibit several unconventional properties. Using first-principles calculations, we predict that strain engineering can be used to control the distribution of topological charges in transition metal silicide candidate CoSi, hosting multifold fermions. We demonstrate that breaking the rotational symmetry of the system, by choosing a suitable strain, destroys the multifold fermions, and at the same time results in the creation of Weyl points. We introduce a low energy effective model to complement the results obtained from density functional calculations. Our findings suggest that strain-engineering is a useful approach to tune topological properties of multifold fermions.