  Quantum materials are defined by the emergence of new properties resulting
from collective quantum effects and by holding promise for their quantum
applications. Novel superconductors, from high-Tc cuprates and iron-based
superconductors to twisted monolayers, exhibit a higher level of emergent
complexity, with a multiband electronic structure playing a pivotal role in
their comprehension and potential applications. Here, we provide a brief
overview of key multiband effects in these superconductors and topological
semimetals, offering guidelines for the theory-assisted development of new
quantum materials and devices.
