Realization of Topological Maxwell Metal Bands with a Superconducting Qutrit

Recently, an interesting new fermion was predicted to emerge in three- or more-fold degenerate points but has yet to be realized in real materials or artificial systems. Here we theoretically propose and experimentally realize a topological Maxwell metal bands with a superconducting qutrit. We do so by mapping the momentum space of condensed-matter models to the tunable parameter space of superconducting quantum circuits. We image a new band structure that consists of three-fold degenerate points dubbed Maxwell points and that is effectively described by the spin-1 Maxwell equations. In addition to dynamically measuring the Chern number of the simulated Maxwell point, we engineer and observe the topological phase transition from the topological Maxwell metal to a trivial insulator. Our work establishes a promising platform to explore complex and novel topological states of matter in controllable quantum systems.