Phase-Factor-Controlled Interaction and Bonding between a Chiral Bobber and a Skyrmion String in the Conical Phase

Abstract

Skyrmion interactions govern the formation of skyrmion lattices, clusters, and particle-like growth patterns. In contrast, the interaction between a chiral bobber and a skyrmion string remains largely unexplored, despite the role of bobbers as intermediate states in skyrmion-string formation and annihilation. Here we show that this interaction is intrinsically phase dependent in the conical phase. Using three-dimensional micromagnetic simulations, we compute the locally relaxed constrained energy landscape as a function of the bobber--skyrmion separation $R$ and the surface phase factor $ϕ_0$. We find that changing $ϕ_0$ qualitatively reshapes the interaction, producing repulsive, attractive, and bonding-like regimes that cannot be reduced to a conventional distance-dependent potential. Real-space analysis shows that this behavior originates from phase-dependent reconstruction of nonaxisymmetric outer distortion shells. The phase-controlled interaction persists over a finite field range and follows the expected top--bottom phase relation of surface-sensitive conical textures. These results identify the conical phase direction, often hidden in projected or thickness-averaged descriptions, as a previously underappreciated degree of freedom in the interaction between skyrmion strings and finite-length chiral textures, as demonstrated here for chiral bobbers.