A quantum material governed by emergent Weyl fermions

In certain crystals, quasiparticles called Weyl fermions emerge from the collective quantum behaviour of electrons. However, these quasiparticles typically coexist with undesired conventional electronic states. After a decade-long search, physicists have engineered a crystal without conventional electronic states and with quantum properties governed entirely by Weyl fermions. Such materials could be useful for detecting and generating terahertz light.