LAUSR

Co3Sn2S2 is a magnetic Weyl semimetal, in which ferromagnetic ordering at 177K is predicted to stabilize Weyl points. We perform temperature and spatial dependent angle–resolved photoemission spectroscopy measurements through the Curie temperature (Tc), which show large band shifts and renormalization concomitant with the onset of magnetism. We argue that Co3Sn2S2 evolves from a Mott ferromagnet below Tc to a correlated metallic state above Tc. To understand the magnetism, we derive a tight–binding model of Co-3dx2−y2 orbitals on the kagome lattice. At the filling obtained by first–principles calculations, this model reproduces the ferromagnetic ground state, and results in the reduction of Coulomb interactions due to cluster effects. Using a disordered local moment simulation, we show how this reduced Hubbard-U leads to a collapse of the bands across the magnetic transition, resulting in a correlated state which carries associated characteristic photoemission signatures that are distinct from those of a simple lifting of exchange splitting. The behavior of topology across Tc is discussed in the context of this description of the magnetism.