# Graphene Hamiltonian

As far as I know, the Hamiltonian of graphene in the Bloch's sums $|A\rangle$ and $|B\rangle$ near the points K or K' is a $2 \times 2$ matrix with the components: $\langle A|H|A\rangle$, $\langle A|H|B\rangle$, $\langle B|H|A\rangle$,$\langle B|H|B\rangle$ which all are parameters (and not variables). But in the Eq.(1) in PHYSICAL REVIEW B 81, 205444 (2010) (http://journals.aps.org/prb/abstract/10.1103/PhysRevB.81.205444) these components are functions and operators in terms of (x,y). Could anyone please tell me how to obtain this formula?