Title: Imaging the electronic density-of-states imprint of nanoscale skyrmion crystals in itinerant magnets
Abstract:
Skyrmions are topologically stable winding configurations of a vector field such as the lattice of spins in a magnet. Magnetic skyrmions, due to their robustness, nanometer scale, and movement under low current densities, have potential applications in future spintronic logic and memory technologies. A widely known form of spin-spin interaction that can stabilize magnetic skyrmions is the Dzyaloshinskii-Moriya interaction, which acts in chiral magnets and other systems in which inversion symmetry is broken. But recently lattices of skyrmions have also been found in inversion-symmetric crystals where the Dzyaloshinskii-Moriya interaction is absent, such as the centrosymmetric magnets Gd₂PdSi₃, GdRu₂Si₂ and GdRu₂Ge₂. Here the stabilizing mechanisms are not yet understood but probably involve spin-spin interactions mediated by itinerant electrons, as in the Rudermann-Kittel-Kasuya-Yosida (RKKY) interaction. These itinerant electrons can be imaged using a scanning tunneling microscope (STM). Here I will describe recent spectroscopic-imaging STM experiments on GdRu₂Si₂ and GdRu₂Ge₂, which each host a rich variety of non-coplanar magnetic phases including multiple skyrmion lattice phases. We see that the electronic density-of-states exhibits intricate textures that change with external field in correspondence with the spin textures. At minimum this supports the itinerant magnetism scenario. I will discuss the microscopic interplay between charge and spin textures in these materials, and what more we can learn about itinerant non-coplanar magnetism, using a purely electronic probe like STM.