Controlling the properties of materials by driving them out of equilibrium is
an exciting prospect that has only recently begun to be explored. In this
Letter we give a striking theoretical example of such materials design: a
tunable gap in monolayer graphene is generated by exciting a particular
optical phonon. We show that the system reaches a steady state whose transport
properties are the same as if the system had a static electronic gap,
controllable by the driving amplitude. Moreover, the steady state displays
topological phenomena: there are chiral edge currents, which circulate a
fractional charge e/2 per rotation cycle, with the frequency set by the
optical phonon frequency
