  Photovoltaic Hall effect -- the Hall effect induced by intense,
circularly-polarized light in the absence of static magnetic fields -- has been
proposed in Phys. Rev. B 79, 081406R (2009) for graphene where a massless Dirac
dispersion is realized. The photovoltaic Berry curvature (a nonequilibrium
extension of the standard Berry curvature) is the key quantity to understand
this effect, which appears in the Kubo formula extended to Hall transport in
the presence of strong AC field backgrounds. Here we elaborate the properties
of the photovoltaic curvature such as the frequency and field strength
dependence in the honeycomb lattice.
