We analyze the dynamics of the helical edge modes of a quantum spin Hall state in the presence of a spatially nonuniform Rashba spin-orbit (SO) interaction. A randomly fluctuating Rashba SO coupling is found to open a scattering channel which causes localization of the edge modes for a weakly screened electron-electron (e-e) interaction. A periodic modulation of the SO coupling, with a wave number commensurate with the Fermi momentum, makes the edge insulating already at intermediate strengths of the e-e interaction. We discuss implications for experiments on edge state transport in a HgTe quantum well.
We analyze a quantum spin Hall device with a point contact connecting two of its edges. The contact supports a net spin tunneling current that can be probed experimentally via a two-terminal resistance measurement. We find that the low-bias tunneling current and the differential conductance exhibit scaling with voltage and temperature that depend nonlinearly on the strength of the electron-electron interaction.
We study the entanglement production in a quantum spin Hall ring geometry where electrons of opposite spins are emitted in pairs from a source and collected in two different detectors. Postselection of coincidence detector events gives rise to entanglement in the system, measurable through correlations between the outcomes in the detectors. We have chosen a geometry such that the entanglement depends on the dynamical phases picked up by the edge states as they move around the ring. In turn, the dependence of the phases on gate potential and Rashba interaction allows for a precise electrical control of the entanglement production in the ring.
Magnetic impurities affect the transport properties of the helical edge
states of quantum spin Hall insulators by causing single-electron
backscattering. We study such a system in the presence of a Rashba spin-orbit
interaction induced by an external electric field, showing that this can be
used to control the Kondo temperature, as well as the correction to the
conductance due to the impurity. Surprisingly, for a strongly anisotropic
electron-impurity spin exchange, Kondo screening may get obstructed by the
presence of a non-collinear spin interaction mediated by the Rashba coupling.
This challenges the expectation that the Kondo effect is stable against
time-reversal invariant perturbations.Comment: 7 pages, 2 figures. Expression for the current operator corrected.
(Conclusions unaffected.) Erratum to be publishe
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