Strain as a topological selector in altermagnetic CrSb

TL;DR

This paper demonstrates that strain and electron localization can systematically control topological phases in the altermagnetic Weyl semimetal CrSb, enabling access to Weyl, Dirac, and triple-point fermions.

Contribution

It introduces strain and Hubbard interaction as new control parameters for topological phases in altermagnets, with a detailed low-energy Hamiltonian model.

Findings

Modest tensile strain stabilizes Dirac crossings and triple-point fermions.

Strain and electron localization can selectively access different topological phases.

CrSb serves as a model system for topological control in altermagnets.

Abstract

Altermagnetism combines fully compensated magnetic order with a magnetic symmetry that relates inequivalent spin sublattices, offering a promising, still underexplored platform for unconventional topological phases. Here we show that both isotropic tensile strain and electron localization, controlled by an effective Hubbard interaction $U_{\text{eff}}$, can act as efficient and systematic topological control parameters in the altermagnetic Weyl semimetal CrSb. While CrSb hosts Weyl fermions at equilibrium, modest tensile strain of 4-5% stabilizes additional symmetry allowed Dirac crossings and triple-point fermions, with further strain selectively favoring the triple-point phase. We propose a 3D low-energy Hamiltonian that captures the interplay between the Hubbard interaction $U$ and the sublattice symmetry of the altermagnet, giving rise to an interaction-driven Dirac crossing. Our results establish CrSb as a model altermagnet in which either strain or electron localization can selectively access and control the distinct topologies inherent to the altermagnets.