Spin excitations of the skyrmion lattice in MnSi

In the less than a decade since skyrmions, topologically-protected three-dimensional spin textures, were originally discovered in MnSi, considerable research efforts have gone towards exploiting their properties for future applications in spintronics. In non-centrosymmetric materials, it is well understood that skyrmions arise due to competition between ferromagnetic exchange and the Dzyaloshinskii-Moriya interaction, which directly relates to their potential for applications, since individual skyrmion size is proportional to the ratio of these interactions. Although the strength of the underlying magnetic interactions can typically be inferred directly from the spin wave dispersion, the mesoscopic size of skyrmions implies a tiny magnetic Brillouin zone, requiring momentum-transfer resolution beyond current state-of-the-art in neutron spectroscopy to resolve the spin waves, an outstanding experimental challenge. Here we overcome this challenge via a new generation of resolution deconvolution, enabling mesoscopic neutron spectroscopy of the spin excitations associated with the skyrmion lattice. The spin wave dispersion and underlying interactions determined in the skyrmion phase of MnSi through this new approach is in excellent agreement with our mean-field Ginzburg-Landau model.