Theory of thermoelectric transport in bilayer graphene*

We present a simple theory of thermoelectric transport in bilayer graphene and report our results for the electrical resistivity, the thermal resistivity, and the Wiedemann-Franz (WF) ratio as functions of doping density and temperature. In contrast with monolayer graphene we obtain finite electrical and thermal resistivities, even in the absence of disorder, i.e. in the extreme hydrodynamic regime. The WF ratio of the clean system reaches a maximal value at the charge-neutrality-point (CNP), and this value increases as a function of temperature. This is in contrast with a perfectly clean monolayer graphene where the WF ratio becomes infinite in the absence of disorder (requiring disorder to be observable).
When disorder is included, we find that the WF ratio in bilayer graphene drops below its maximal value, resulting in an interesting non-monotonic behavior as a function of doping density in the vicinity of the CNP.