  It is well-known that the dynamics of low energy electron in graphene
honeycomb lattice near the K/K' points can be described, in tight-binding
approximation, by 2+1 massless Dirac equation. Graphene's spin equivalent,
"pseudospin", arises from the degeneracy introduced by the honeycomb lattice's
two inequivalent atomic sites per unit cell. Mecklenburg and Regan (Phys. Rev.
Lett. 106 (2011), 116803) have shown that, contrary to the common view, the
pseudospin has all attributes of real angular momentum. In some circumstances,
the internal symmetries can produce an important contribution to angular
momentum. This phenomenon has been known for many years in particle physics and
called "spin from isospin". We show that similar mechanism works in the case of
lattice pseudospin.
