Edge accumulation and currents of moment in 2D topological insulators

The Letter is analyzing bulk spin (moment) currents and spin (moment) accumulation at edges of a 2D topological insulator taking into account reflection from edges. Accumulation occurs only at edge states, which distinguish topological insulators from conventional ones. The band continuum can support the transverse bulk spin (moment) current, but it does not governed by the topological Chern number and may exist in a conventional insulator. There is no edge accumulation related with bulk currents.