Visualizing the origin of bulk metallicity in Kondo insulators
Most materials either conduct electricity (e.g. metals) or don't (insulators). Strangely, the Kondo-lattice compound SmB6 was recently discovered to be both metallic and insulating at the same time, depending on the measurement taken. Specifically, it displays a de Haas-van Alphen effect characteristic of a metallic Fermi surface, while simultaneously exhibiting a divergent electrical resistivity. As you might expect, this discovery generated a lot of interest among physicists, but little consensus. In this talk, I will introduce a new technique to measure electric charge with single-atom precision using a scanning tunneling microscope [1]. Our images of SmB6 reveal a landscape of small metallic puddles where electrons can move freely, while the rest of the material acts as an insulator. Our results suggest that the de Haas-van Alphen measurements may arise from these metallic puddles, although we cannot exclude other explanations.