Credit: Image courtesy of Massachusetts Institute of Technology
Scientists predicted and directly measured electrons in a semimetal. The electrons were behaving like elusive massless particles. Shining a circularly polarized light beam (pink spiral) onto a tantalum-arsenide semimetal (ball-and-stick crystal model) generates an electrical current (green arrow). Remarkably, the direction of the current flow changes by switching the light’s polarization from right-handed to left-handed, proving the handedness of exotic Weyl fermions.