13,984 research outputs found
Quantum Hall Effect in Thin Films of Three-Dimensional Topological Insulators
We show that a thin film of a three-dimensional topological insulator (3DTI)
with an exchange field is a realization of the famous Haldane model for quantum
Hall effect (QHE) without Landau levels. The exchange field plays the role of
staggered fluxes on the honeycomb lattice, and the hybridization gap of the
surface states is equivalent to alternating on-site energies on the AB
sublattices. A peculiar phase diagram for the QHE is predicted in 3DTI thin
films under an applied magnetic field, which is quite different from that
either in traditional QHE systems or in graphene.Comment: 4 pages, 4 figure
A topological look at the quantum spin Hall state
We propose a topological understanding of the quantum spin Hall state without
considering any symmetries, and it follows from the gauge invariance that
either the energy gap or the spin spectrum gap needs to close on the system
edges, the former scenario generally resulting in counterpropagating gapless
edge states. Based upon the Kane-Mele model with a uniform exchange field and a
sublattice staggered confining potential near the sample boundaries, we
demonstrate the existence of such gapless edge states and their robust
properties in the presence of impurities. These gapless edge states are
protected by the band topology alone, rather than any symmetries.Comment: 5 pages, 4 figure
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