  Periodic driving fields can induce topological phase transitions, resulting
in Floquet topological phases with intriguing properties such as very large
Chern numbers and unusual edge states. Whether such Floquet topological phases
could generate robust edge state conductance much larger than their static
counterparts is an interesting question. In this paper, working under the
Keldysh formalism, we study two-lead transport via the edge states of
irradiated quantum Hall insulators using the method of recursive
Floquet-Green's functions. Focusing on a harmonically-driven Hofstadter model,
we show that quantized Hall conductance as large as $8e^2/h$ can be realized,
but only after applying the so-called Floquet sum rule. To assess the
robustness of edge state transport, we analyze the DC conductance,
time-averaged current profile and local density of states. It is found that
co-propagating chiral edge modes are more robust against disorder and defects
as compared with the remarkable counter-propagating edge modes, as well as
certain symmetry-restricted Floquet edge modes. Furthermore, we go beyond the
wide-band limit, which is often assumed for the leads, to study how the
conductance quantization (after applying the Floquet sum rule) of Floquet edge
states can be affected if the leads have finite bandwidths. These results may
be useful for the design of transport devices based on Floquet topological
matter.
