Magnons reveal topology and dynamics of a skyrmion crystal

Abstract

Although individual skyrmions are topologically protected objects, their cooperative crystalline order is fragile, easily disrupted by thermal fluctuations or other external perturbations. Probing the internal dynamics of such a crystal is both compelling and challenging, as its intricate and delicate spin texture must remain stable during measurement. Here, we engineer a nanoscale graphene junction hosting a skyrmion Wigner crystal, embedded between magnon emitters and detectors. The skyrmion crystal geometry leaves a striking imprint on magnon transport: as the gate voltage is varied, near-periodic windows of sharp fluctuations in magnon count are detected across the entire sample. We develop an interpretation that this results from skyrmions being added one by one to a quasi-one-dimensional array. Each burst of the fluctuations thus corresponds to the entry of an additional skyrmion, during which the lattice stiffness reduces. The impinging magnons induce and act as a probe of non-equilibrium collective dynamics of the crystal. These results establish a real-space probe of topological spin textures in quantum Hall-type insulating ground states via magnon transport and open opportunities to explore correlated, topologically ordered phases in moire and multilayer graphene systems.