Correlation induced magnetic topological phases in the mixed-valence compound SmB6

An insulator-to-metal phase transition in rare-earth mixed-valence compounds is shown to be driven by magnetic correlations, which are enhanced under external pressure. Condensation of the spin exciton mode gives rise to a magnetic metal with distinct band topology and surface states. It is shown that magnetic instability is also triggered by lowering the cubic symmetry, thus explaining the surface magnetism in SmB${}_{6}$.