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Silvestrov P.G.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig | Brouwer P.W.,Free University of Berlin
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

The current through a helical edge state of a quantum spin Hall insulator may be fully transmitted through a magnetically gapped region due to a combination of spin-transfer torque and spin pumping [Meng, Phys. Rev. B 90, 205403 (2014)PRBMDO1098-012110.1103/PhysRevB.90.205403]. Using a scattering approach, we here argue that in such a system the current is effectively carried by electrons with energies below the magnet-induced gap and well below the Fermi energy. This has striking consequences, such as the absence of shot noise, an exponential suppression of thermal noise, and an obstruction of thermal transport. For two helical edges covered by the same quantum magnet, the device can act as a robust noiseless current splitter. © 2016 American Physical Society. Source


Probst B.,TU Braunschweig | Virtanen P.,Aalto University | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We investigate a Zeeman-split quantum dot (QD) containing a single spin 1/2 weakly coupled to a helical Luttinger liquid (HLL) within a generalized master equation approach. The HLL induces a tunable magnetization direction on the QD controlled by an applied bias voltage when the quantization axes of the QD and the HLL are noncollinear. The backscattering conductance (BSC) in the HLL is finite and shows a resonance feature when the bias voltage equals the Zeeman energy in magnitude. The observed BSC asymmetry in bias voltage directly reflects the quantization axis of the HLL spin. © 2015 American Physical Society. ©2015 American Physical Society. Source


Strom A.,TU Braunschweig | Johannesson H.,Gothenburg University | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

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. © 2015 American Physical Society. Source


Schroer A.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We model a superconducting p-n junction in which the n and the p sides are contacted through two optical quantum dots (QDs), each embedded into a photonic nanocavity. Whenever a Cooper pair is transferred from the n side to the p side, two photons are emitted. When the two electrons of a Cooper pair are transported through different QDs, polarization-entangled photons are created, provided that the Cooper pairs retain their spin singlet character while being spatially separated on the two QDs. We show that a Clauser-Holt-Shimony-Horne (CHSH) Bell-type measurement is able to detect the entanglement of the photons over a broad range of microscopic parameters, even in the presence of parasitic processes and imperfections. © 2015 American Physical Society. Source


Park S.,TU Braunschweig | Recher P.,TU Braunschweig | Recher P.,Laboratory for Emerging Nanometrology Braunschweig
Physical Review Letters | Year: 2015

A phase from an adiabatic exchange of Majorana bound states (MBS) reveals their exotic anyonic nature. For detecting this exchange phase, we propose an experimental setup consisting of a Corbino geometry Josephson junction on the surface of a topological insulator, in which two MBS at zero energy can be created and rotated. We find that if a metallic tip is weakly coupled to a point on the junction, the time-averaged differential conductance of the tip-Majorana coupling shows peaks at the tip voltages eV=±(α-2πl)/TJ, where α=π/2 is the exchange phase of the two circulating MBS, TJ is the half rotation time of MBS, and l an integer. This result constitutes a clear experimental signature of Majorana fermion exchange. © 2015 American Physical Society. Source

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