Spin Hall angle in single-layer graphene

We investigate the spin Hall effect in a single-layer graphene device with disorder and interface-induced spin-orbit coupling. Our graphene device is connected to four semi-infinite leads that are embedded in a Landauer-Buttiker setup for quantum transport. We show that the spin Hall angle of graphene devices exhibits mesoscopic fluctuations that are similar to metal devices. Furthermore, the product between the maximum spin Hall angle deviation and dimensionless longitudinal conductivity follows a universal relationship theta(sH) x sigma = 0.18. Finally, we compare the universal relation with recent experimental data and numerically exact real-space simulations from the tight-binding model.