Curvature-Controlled Topological Magnon Phases in a Folded Kagome Lattice

Abstract

We show that geometric curvature, encoded in the folding angle between two corner-sharing triangles on a kagome lattice, provides a continuous tuning knob for topological magnon phase. Starting from an extended spin Hamiltonian with exchange, Dzyaloshinskii-Moriya (DM) interaction, and a higher-order bow-tie coupling of scalar chiralities, we derive the chirality-mediated hopping amplitude, which depends on the folding and spin canting of the bow-tie triangles. At small folding and canting angles, the bow-tie coupling surpasses DM, establishing a curvature-dominated regime. These results establish curvature as an intrinsic geometric control parameter for topological magnonics and reveal a direct analogy with chirality-induced spin selectivity in molecular systems, pointing to a unified mechanism for chirality driven transport across scales. The mechanism is particularly relevant for chiral crystals where the DM interaction is weak or forbidden by symmetry, as in systems with a six-fold screw axis.