  Both spin and orbital degrees of freedom contribute to the magnetic moment of
isolated atoms. However, when inserted in crystals, atomic orbital moments are
quenched because of the lack of rotational symmetry that protects them when
isolated. Thus, the dominant contribution to the magnetization of magnetic
materials comes from electronic spin. Here we show that nanoislands of quantum
spin Hall insulators can host robust orbital edge magnetism whenever their
highest occupied Kramers doublet is singly occupied, upgrading the spin edge
current into a charge current. The resulting orbital magnetization scales
linearly with size, outweighing the spin contribution for islands of a few nm
in size. This linear scaling is specific of the Dirac edge states and very
different from Schrodinger electrons in quantum rings. Modelling Bi(111)
flakes, whose edge states have been recently observed, we show that orbital
magnetization is robust with respect to disorder, thermal agitation, shape of
the island and crystallographic direction of the edges, reflecting its
topological protection.
