Holography of the Dirac Fluid in Graphene with two currents
  Recent experiments have uncovered evidence of the strongly coupled nature of the graphene: the Wiedemann-Franz law is violated by up to a factor of 20 near the charge neutral point. We describe this strongly-coupled plasma by a holographic model in which there are two distinct conserved U(1) currents. We find that our analytic results for the transport coefficients for two current model have a significantly improved match to the density dependence of the experimental data than the models with only one current. The additive structure in the transports coefficients plays an important role. We also suggest the origin of the two currents. 
Yunseok Seo, Geunho Song, Philip Kim, Subir Sachdev, Sang-Jin Sin
hep-th cond-mat.str-el