2D transport and screening in topological insulator surface states

We study disorder effects on the surface states of the topological insulator Bi$_2$Se$_3$ close to the topologically protected crossing point. Close to charge neutrality, local fluctuations in carrier density arising from the random charged disorder in the environment result in electron and hole puddles that dominate the electronic properties of these materials. By calculating the polarizability of the surface state using the random phase approximation, and determining the characteristics of puddles using the self-consistent approximation, we find that band asymmetry plays a crucial role in determining experimentally measured quantities including the conductivity and the puddle autocorrelation length.