Transport Signatures of Fractional Fermions in Rashba Nanowires

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We investigate numerically the possibility to detect the spatial profile of Majorana fermions (MFs) by using STM tips that are made of either normal or superconducting material. In both cases, we are able to resolve the localization length and the oscillation period of the MF wave function. We show that the tunneling between the substrate and the tip, necessary to get the information on the wave-function oscillations, has to be weaker in the case of a superconducting probe. In the strong tunneling regime, the differential conductance saturates making it more difficult to observe the exponential decay of MFs. The temperature broadening of the profile is strongly suppressed in the case of the superconducting tip resulting, generally, in better resolution.

Section: Discussionmentioning

confidence: 99%

Tomography of Majorana fermions with STM tips

Chevallier

Klinovaja

2016

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“…We have numerically obtained the two-terminal conductance G=dI/dV b , with I the charge current and V b the applied bias voltage, of the above described hybrid structure by employing the standard scattering theory 37 , with the help of the recursive Green's function techniques 38 , similarly to what has been done in our previous work 14,39,40 . We calculate G as a function of the gate potential V g (at fixed zero bias V b = 0), but the results should be essentially identical to the conductance measured as a function of bias voltage V b (measured at fixed zero gate potential V g = 0).…”

Section: Modelmentioning

confidence: 99%

Conductance behavior in nanowires with spin-orbit interaction: A numerical study

Rainis

Loss

2014

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We consider electronic transport through semiconducting nanowires (W) with spin-orbit interaction (SOI), in a hybrid N-W-N setup where the wire is contacted by normal-metal leads (N). We investigate the conductance behavior of the system as a function of gate and bias voltage, magnetic field, wire length, temperature, and disorder. The transport calculations are performed numerically and are based on standard recursive Green's function techniques. In particular, we are interested in understanding if and how it is possible to deduce the strength of the SOI from the transport behavior. This is a very relevant question since so far no clear experimental observation in that direction has been produced. We find that the smoothness of the electrostatic potential profile between the contacts and the wire plays a crucial role, and we show that in realistic regimes the N-W-N setup may mask the effects of SOI, and a trivial behavior with apparent vanishing SOI is observed. We identify an optimal parameter regime, with neither too smooth nor too abrupt potentials, where the signature of SOI is best visible, with and without Fabry-Pérot oscillations, and is most resilient to disorder and temperature effects.

“…An analogous bound state occurs also at the right end of the constriction. These zero-energy bound states are examples of fractional fermions of the Jackiw-Rebbi type [67][68][69][70][71][72] and possess non-Abelian braiding statistics [70].…”

mentioning

confidence: 99%

“…If the magnetization rotates not exactly by π but by some finite angle χ, the bound state moves away from zero energy, E = −∆ x cos(χ/2) for 0 < χ < 2π. The domain wall localizes the charge e/2 only for χ = π, which brings us back to the fractional fermions of the Jackiw-Rebbi type [67][68][69][70][71][72].…”

mentioning

confidence: 99%

Fractional charge and spin states in topological insulator constrictions

Klinovaja

Loss

2015

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We investigate theoretically properties of two-dimensional topological insulator constrictions both in the integer and fractional regimes. In the presence of a perpedicular magnetic field, the constriction functions as a spin filter with near-perfect efficiency and can be switched by electric fields only. Domain walls between different topological phases can be created in the constriction as an interface between tunneling, magnetic fields, charge density wave, or electron-electron interactions dominated regions. These domain walls host non-Abelian bound states with fractional charge and spin and result in degenerate ground states with parafermions. If a proximity gap is induced bound states give rise to an exotic Josephson current with 8π-peridiodicity.