Holography of the Dirac Fluid in Graphene with Two Currents

Recent experiments have uncovered evidence of the strongly coupled nature of 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 the 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 transport coefficients plays an important role. We also suggest the origin of the two currents.

Figure 1

Theory vs data: (a) density plot of $\sigma$, and (b) that of $\kappa$. Red circles are for data used in [11, 13], dashed lines are for the one current model, and real lines are for the two current model. The blue color is for the Fermi liquid regime and the near charge neutral point is the Dirac fluid regime, where our theory works. Color grading is given to guide the eye.