Electron states near graphene edge

The band structure of graphene near the Fermi surface is often well described by the effective mass approximation. In this approach electron wave function obeys the Dirac-type equation. To describe a number of effects it is necessary to supplement the equation with boundary conditions. Using the Hemiticity and the time reversal symmetry we derive the phenomenological boundary conditions for a multicomponent effective wave function. The boundary conditions in the case of smooth crystalline potential near the edge are parameterized in terms of a real phenomenological constant that describes a general type edge. The edge states spectra (i.e. Tamm states spectra) for semi-infinite graphene are analyzed.