Chirality Sum Rule in Graphene Multilayers

We show that the low energy electronic structure of arbitrarily stacked graphene multilayers with nearest-neighbor interlayer tunneling consists solely of chiral pseudospin doublets. Although the number of doublets in an $N$-layer system depends on the stacking sequence, the pseudospin chirality sum is always $N$. It follows that $N$-layer stacks always have $N$ distinct Landau levels at $E=0$ for each spin and valley, and that the quantized Hall conductivity $\sigma_{xy} = \pm(4 e^2/h)(N/2+n)$ where $n$ is a non-negative integer.