Magnonic topological insulator realized in 2D magnetic skyrmion crystals

Abstract

With the concept of topological order of electronic states in crystals being proposed, the pursuit of topological phases in various systems has become an important subject of modern physical science. The existence of antisymmetric Dzyaloshinskii–Moriya interaction caused by spin–orbit coupling in magnetic systems leads to the non-reciprocal propagation of magnons, which is a key factor to realize the magnonic analog of an electronic topological insulator (TI). Here, a two-dimensional magnetic skyrmion crystal (SkX) is introduced as a platform for realizing magnonic TI. It is numerically demonstrated that nonchiral and chiral edge states could exist in different magnonic bandgaps. The nonchiral edge magnons can propagate to both directions simultaneously along the boundary of the SkX with different wavelengths and group velocities. By contrast, chiral edge magnons are topologically protected, resulting in the unidirectional propagation along the boundaries and the robustness against defects or disorders. Furthermore, the chirality and the presence of edge magnons can be manipulated by the polarity of skyrmions and the width of the second magnonic bandgap via the magnetic field. Our findings could provide a skyrmionic paradigm for investigating topological magnonics and even quantum magnonics.