Metallic chemical potentials in an insulating topological state

Controlling the density of electrons inside an insulator via the chemical potential is a cornerstone of modern electronics, enabling the electrical conductivity of semiconductors and the emergence of fascinating new properties linked with electronic correlations. The compound SmB6 has drawn widespread attention in recent years as the first insulator to feature both strong electronic correlations and topological quantum order1-7, potentially enabling a host of new phenomenologies as charge density is modified. However, chemical potential has not been experimentally controlled in studies to date of the electronic structure. Here we present an angle-resolved photoemission spectromicroscopy (μ-ARPES) study of SmB6 alloys, using the natural inhomogeneity of sample surfaces to create the analogue of a multi-dimensional doping series. The role of electronic correlations is observed in the interplay of the topologically ordered conducting states with one another and with the chemical potential. Higher doping is found to result in the transformation of these interdependencies as the disorder from impurities erodes quantum coherence. These findings set the stage for a holistic understanding of the interplay between strong correlations and topological features in the electron system. Moreover, they validate recent analyses suggesting that the electronic structure of SmB6 can present the key hallmarks of conventional electron doping, such as a Fermi surface, while nonetheless preserving long-range insulating character in electrical transport measurements8-10.