APS/Alan Stonebraker

Figure 1: Photoemission can be used to detect the chirality of electron wave functions in a doped single layer of graphene. The shaded region in each sketch indicates the part of the graphene electron energy spectrum (the “Dirac cones”) that is accessible for a particular optical polarization: (a) right-circularly polarized (RCP); (b) vertically polarized (VP); (c) left-circularly polarized (LCP); and (d) horizontally polarized (HP). The accessible regions are determined by dipole selection rules. Arrows on the cones indicate the chirality of accessible electrons. The vertical arrow in (a) indicates the binding energy relative to the Fermi level. The phase angle $θ$ is depicted at the Dirac point, where the cones meet.