Magnetic-Field-Independent Subgap States in Hybrid Rashba Nanowires

Jünger, Christian; Delagrange, R.; Chevallier, Denis; Lehmann, Sebastian; Dick, Kimberly A.; Thelander, Claes; Klinovaja, Jelena; Loss, Daniel; Baumgärtner, A.; Schönenberger, Christian

doi:10.1103/physrevlett.125.017701

Cited by 50 publications

(24 citation statements)

References 43 publications

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“…Actually, this complexity in experiments can be attributed to the intrinsic chemical inhomogeneity which comes from the nonuniform substitution of Se atoms, unavoidable defects, or excess iron atoms due to the special stoichiometry of Fe(Te,Se), as validated by scanning topography [82]. Regarding this "dirty" composition of Fe(Te,Se) SC, it is thus an urgent question to clarify whether the observed zero-energy states in Fe(Te,Se) are MBSs, which can be used as robust topological qubits, or whether this ZBP could be attributed to trivial Andreev bound states (ABSs) as was demonstrated in other MBS platforms [83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98][99][100][101].…”

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confidence: 99%

Zero-energy Andreev bound states in iron-based superconductor Fe(Te,Se)

Hou,

Klinovaja

2021

Preprint

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Majorana bound states have been predicted to exist in vortices of topological superconductors (SC). A realization of the Fu-Kane model, based on a three-dimensional topological insulator brought into proximity to an s-wave SC, in iron-based SC Fe(Te,Se) has attracted strong interest after pronounced zero-energy bias peaks were observed in several experiments. Here, we show that, by taking into account inhomogeneities of the chemical potential or the presence of potential impurities on the surface of Fe(Te,Se), the emergence of these zero-energy bias peaks can be explained by trivial Andreev bound states (ABSs) whose energies are close to zero. Our numerical simulations reveal that the ABSs behave similarly to Majorana bound states. ABSs are localized only on the, say, top surface and cannot be distinguished from their topological counterparts in transport experiments performed with STM tips. Thus, such ABSs deserve a careful investigation of their own.

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confidence: 99%

Zero-energy Andreev bound states in iron-based superconductor Fe(Te,Se)

Hou,

Klinovaja

2021

Preprint

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“…Recently, epitaxially defined QDs, where the confinement is obtained by two NW segments in the wurtzite phase in otherwise zinc blende InAs NW, [17] were employed for tunnel spectroscopy of the local density of states in proximitized NWs. [18,19] In these experiments, one can see that the proximity-induced gap appears sharply with gate voltage at an electron density for which the superconducting coherence length becomes larger than the distance between the integrated QD and the region covered by the superconductor. We will refer to this nanowire section in the following as the 'lead segment'.…”

Section: Introductionmentioning

confidence: 80%

Spectroscopy of the local density-of-states in nanowires using integrated quantum dots

Thomas,

Nilsson,

Ciaccia

et al. 2021

Preprint

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In quantum dot (QD) electron transport experiments additional features can appear in the differential conductance dI/dV that do not originate from discrete states in the QD, but rather from a modulation of the density-of-states (DOS) in the leads. These features are particularly pronounced when the leads are strongly confined low dimensional systems, such as in a nanowire (NW) where transport is one-dimensional and quasi-zero dimensional lead-states can emerge. In this paper we study such lead-states in InAs NWs. We use a QD integrated directly into the NW during the epitaxial growth as an energetically and spatially well-defined tunnel probe to perform dI/dV spectroscopy of discrete bound states in the 'left' and 'right' NW lead segments. By tuning a sidegate in close proximity of one lead segment, we can distinguish transport features related to the modulation in the lead DOS and to excited states in the QD. We implement a non-interacting capacitance model and derive expressions for the slopes of QD and lead resonances that appear in two-dimensional plots of dI/dV as a function of source-drain bias and gate voltage in terms of the different lever arms determined by the capacitive couplings. We discuss how the interplay between the lever arms affect the slopes. We verify our model by numerically calculating the dI/dV using a resonant tunneling model with three non-interacting quantum dots in series. Finally, we used the model to describe the measured dI/dV spectra and extract quantitatively the tunnel couplings of the lead segments. Our results constitute an important step towards a quantitative understanding of normal and superconducting subgap states in hybrid NW devices.

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“…In addition to the direct measurement of MBSs, an independent signature of the topological phase transition can be obtained by focusing on the spin and charge properties of our system [66][67][68][69]. Such studies can help to exclude the possibility of identifying a trivial phase as topological due to the observation of a stable zero-energy bias peak arising from the trivial Andreev bound state [70][71][72][73][74][75][76][77][78][79]. The required techniques have already been successfully employed in recent experimental measurements [64,[80][81][82][83][84][85][86].…”

Section: Spin and Charge Polarizationmentioning

confidence: 99%

Majorana bound states in topological insulators with hidden Dirac points

Schulz

Plekhanov

Loss

et al. 2020

Phys. Rev. Research

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We address the issue of whether it is possible to generate Majorana bound states at the magneticsuperconducting interface in two-dimensional topological insulators with hidden Dirac points in the spectrum. In this case, the Dirac point of edge states is located at the energies of the bulk states such that two types of states are strongly hybridized. Here, we show that well-defined Majorana bound states can be obtained even in materials with a hidden Dirac point provided that the width of the magnetic strip is chosen to be comparable with the localization length of the edge states. The obtained topological phase diagram allows one to extract precisely the position of the Dirac point in the spectrum. In addition to standard zero-bias peak features caused by Majorana bound states in transport experiments, we propose to supplement future experiments with measurements of charge and spin polarization. In particular, we demonstrate that both observables flip their signs at the topological phase transition, thus providing an independent signature of the presence of topological superconductivity. All features remain stable against substantially strong disorder.

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Magnetic-Field-Independent Subgap States in Hybrid Rashba Nanowires

Cited by 50 publications

References 43 publications

Zero-energy Andreev bound states in iron-based superconductor Fe(Te,Se)

Zero-energy Andreev bound states in iron-based superconductor Fe(Te,Se)

Spectroscopy of the local density-of-states in nanowires using integrated quantum dots

Majorana bound states in topological insulators with hidden Dirac points

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