Spin orientation and strain tuning of orbital-selective Dirac gap in the itinerant kagome metal DyMn6Sn6

Abstract

Kagome magnets in the 166 family provide a fertile platform for coupling magnetic order with topological electronic states, particularly DyMn6Sn6, which hosts a natural spin orientation. Using density functional theory+U calculations, we establish that the Mn-3d electrons are weakly correlated, while the Dy-4f states reside far below the Fermi level (EF), having negligible impact on the low-energy electronic structures. We identify two Dirac points with contrasting sensitivities to Mn spin orientation. The gap of the Dirac point above EF follows a cos θ scaling determined by the ⟨ψ|LzSz|ψ⟩ spin–orbit coupling term, whereas the Dirac point below EF remains nearly invariant due to its d3z2−r2 orbital character. Furthermore, isotropic strain is shown to effectively tune the Dirac and flatbands, with lattice expansion enhancing the magnetization via the Stoner mechanism. Our results demonstrate that spin reorientation and strain are effective “knobs” for engineering topological phases in kagome systems.