1302.2284 (Motohiko Ezawa)

Half-Integer Quantum Hall Effects and Single Dirac-Cone States in
Silicene    [PDF]

Motohiko Ezawa

The massless Dirac electron is expected to display half-integer quantum Hall effect (QHE) at the filling factor $\nu =\pm 1/2,\pm 3/2,\pm 5/2,... $, reflecting the parity anomaly. However, it has so far been unable to materialize such a series due to the fermion doubling problem inherent to the chiral symmetric lattice system. For instance, the QHE in graphene displays a series $\nu =\pm 2,\pm 6,\pm 10,... $ because of the 4-fold degeneracy of each Landau level. We demonstrate that the half-integer series $\nu =\pm 1/2,\pm 3/2,\pm 5/2,... $ can arise in silicene, which is a silicon cousin of graphene, when we break the chiral, time-reversal and inversion symmetries all together by applying electric field and photo-irradiation simultaneously. A prominent hallmark is the emergence of a single Dirac-cone (SDC) state, which contains one massless Dirac cone and three massive Dirac cones in the Brillouin zone. A SDC state is a topologically protected semimetal since it emerges along the boundary between two distinctive topological insulators. The half-integer QHE is predicted to appear in such a SDC state.

View original: http://arxiv.org/abs/1302.2284