86 research outputs found
Multiprobe quantum spin Hall bars
We analyze electron transport in multiprobe quantum spin Hall (QSH) bars
using the B\"{u}ttiker formalism and draw parallels with their quantum Hall
(QH) counterparts. We find that in a QSH bar the measured resistance changes
upon introducing side voltage probes, in contrast to the QH case. We also study
four- and six-terminal geometries and derive the expressions for the
resistances. For these our analysis is generalized from the single-channel to
the multi-channel case and to the inclusion of backscattering originating from
a constriction placed within the bar.Comment: 6 pages, 5 figure
Spin-pumping and inelastic electron tunneling spectroscopy in topological insulators
We demonstrate that a quantum spin Hall current, spontaneously generated at
the edge of a two-dimensional topological insulator, acts as a source of
spin-pumping for a magnetic impurity with uniaxial anisotropy. One can then
manipulate the impurity spin direction by means of an electrical current
without using either magnetic electrodes or an external magnetic field.
Furthermore we show that the unique properties of the quantum spin Hall
topological state have profound effects on the inelastic electron tunneling
spectrum of the impurity. For low current densities inelastic spin-flip events
do not contribute to the conductance. As a consequence the conductance steps,
normally appearing at voltages corresponding to the spin excitations, are
completely suppressed. In contrast an intense current leads to spin pumping and
generates a transverse component of the impurity spin. This breaks the
topological phase yielding to the conductance steps.Comment: Updated text, added figure, published versio
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