Vectorial field STM study on a topological and correlated magnet*

We utilize a combination of vector magnetic field and high resolution scanning tunneling microscopy to visualize the electronic response to vector magnetization in an iron-tin topological magnet. Atomically resolved images of the cleaving surface show both an iron-tin kagome lattice and a tin honeycomb lattice. We find that a quantum electronic state from the kagome lattice couples strongly and 3D-anisotropically with the magnetization. Moreover, the orbital symmetry of this quantum state can be controlled by the vector magnetic field. These large and anisotropic electronic responses cannot be explained by conventional Zeeman physics, but strongly point to a topological origin. These results will help us understand the interplay between magnetism and topological order in a correlated magnet.