7 research outputs found
Tunable quantum spin Hall effect in double quantum wells
The field of topological insulators (TIs) is rapidly growing. Concerning
possible applications, the search for materials with an easily controllable TI
phase is a key issue. The quantum spin Hall effect, characterized by a single
pair of helical edge modes protected by time-reversal symmetry, has been
demonstrated in HgTe-based quantum wells (QWs) with an inverted bandgap. We
analyze the topological properties of a generically coupled HgTe-based double
QW (DQW) and show how in such a system a TI phase can be driven by an
inter-layer bias voltage, even when the individual layers are non-inverted. We
argue, that this system allows for similar (layer-)pseudospin based physics as
in bilayer graphene but with the crucial absence of a valley degeneracy.Comment: 9 pages, 8 figures, extended version (accepted Phys. Rev. B
~Green's function topology of Majorana wires
We represent the ~topological invariant characterizing a one
dimensional topological superconductor using a Wess-Zumino-Witten dimensional
extension. The invariant is formulated in terms of the single particle Green's
function which allows to classify interacting systems. Employing a recently
proposed generalized Berry curvature method, the topological invariant is
represented independent of the extra dimension requiring only the single
particle Green's function at zero frequency of the interacting system.
Furthermore, a modified twisted boundary conditions approach is used to
rigorously define the topological invariant for disordered interacting systems.Comment: final versio