Fermionic microscope watches individual atoms in transition

Researchers in the US have taken images of individual atoms in an ultracold fermionic gas as it makes the transition from a metallic phase to a band insulator and then to a Mott insulator. This is the first study of such a transition in a fermionic gas to be made with single-site and single-particle resolution. While such experiments are routinely done using ultracold bosonic atoms, doing the same with fermions is more challenging because they are difficult to cool. However, the rewards for physicists could be greater because fermionic atoms are a closer match to electrons in a solid, and therefore such experiments could shed light on poorly understood solid systems such as high-temperature superconductors.