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Orbital Magnetization of Quantum Spin Hall Insulator Nanoparticles
journal contribution
posted on 2015-09-09, 00:00 authored by P. Potasz, J. Fernández-RossierBoth 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. By modeling 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.