Near-zero-energy end states in topologically trivial spin-orbit coupled superconducting nanowires with a smooth confinement

Kells, Graham; Meidan, Dganit; Brouwer, Piet W.

doi:10.1103/physrevb.86.100503

Cited by 370 publications

(249 citation statements)

References 32 publications

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“…Kondo physics can be observed in normal superconductor nanowires as well [33,34]. Furthermore, nearly zero-energy Andreev states [35,36] or weak antilocalization [37] effects are possible sources of zero-bias anomaly in normal superconductor nanowires. There are other suggestions to detect Majorana zero-energy states in Josephson junctions and rings [38][39][40][41][42][43][44][45][46].…”

Section: Introductionmentioning

confidence: 99%

Thermoelectrical detection of Majorana states

et al. 2014

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We discuss the thermoelectrical properties of nanowires hosting Majorana states. For a Majorana nanowire directly coupled to two normal reservoirs the thermopower always vanishes regardless of the value of the Majorana overlap parameter ε M , due to the particle-hole symmetric nature of the Majorana states. This situation changes drastically if a quantum dot (QD) is inserted to break the particle-hole symmetry. Then, the Majorana-side-coupled QD system exhibits a different behavior for the thermopower depending on the value of ε M . The thermopower globally reverses its sign when the half-fermionic nature of the Majorana state is relevant, i.e., for ε M k B T b , where T b is the background temperature. For large overlap, ε M k B T b , on the other hand, the Seebeck coefficient behaves similarly to that in a resonant level system. The sign change of the thermopower and the fact that both the electrical and thermal conductances reach their half-fermionic value when Majorana physics are maximal could serve as a proof of the existence of Majorana states in nanowires.

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Section: Introductionmentioning

confidence: 99%

Thermoelectrical detection of Majorana states

et al. 2014

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“…Unfortunately, the outcome of the simplest detection protocol for MBSs in NW devices [20][21][22], detection of subgap zero modes through zero-bias anomalies in transport [23][24][25][26][27][28], can be obscured, or even mimicked, by other effects [29][30][31][32][33][34][35][36]. As a result, there is no clear consensus yet on whether MBSs have been observed or not in NWs.…”

Section: Introductionmentioning

confidence: 99%

SNS junctions in nanowires with spin-orbit coupling: Role of confinement and helicity on the subgap spectrum

et al. 2015

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We study normal transport and the subgap spectrum of superconductor-normal-superconductor (SNS) junctions made of semiconducting nanowires with strong Rashba spin-orbit coupling. We focus, in particular, on the role of confinement effects in long ballistic junctions. In the normal regime, scattering at the two contacts gives rise to two distinct features in conductance: Fabry-Perot resonances and Fano dips. The latter arise in the presence of a strong Zeeman field B that removes a spin sector in the leads (helical leads), but not in the central region. Conversely, a helical central region between nonhelical leads exhibits helical gaps of half-quantum conductance, with superimposed helical Fabry-Perot oscillations. These normal features translate into distinct subgap states when the leads become superconducting. In particular, Fabry-Perot resonances within the helical gap become parity-protected zero-energy states (parity crossings), well below the critical field B c at which the superconducting leads become topological. As a function of Zeeman field or Fermi energy, these zero modes oscillate around zero energy, forming characteristic loops, which evolve continuously into Majorana bound states as B exceeds B c . The relation with the physics of parity crossings of Yu-Shiba-Rusinov bound states is discussed.

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“…Spatial sharpness of the boundary region between the superconductor and the topological or semi-conducting material is also essential in order to distinguish between the near-zero-energy end states originating in Andreev bound states, and the Majorana zero energy modes in the topological case [14]. Since this boundary is generally created by gating in the experiments, its unavoidable gradual spatial change adds more uncertainty to the interpretation of the observed ZBCPs as due to the Majorana modes [10,11,15].…”

Section: Introductionmentioning

confidence: 99%

Magnetoresistance, Gating and Proximity Effects in Ultrathin NbN-Bi2Se3 Bilayers

Koren

2017

Condensed Matter

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Ultrathin Bi 2 Se 3 -NbN bilayers comprise a simple proximity system of a topological insulator and an s-wave superconductor for studying gating effects on topological superconductors. Here we report on 3 nm thick NbN layers of weakly connected superconducting islands, overlayed with 10 nm thick Bi 2 Se 3 film which facilitates enhanced proximity coupling between them. Resistance versus temperature of the most resistive bilayers shows insulating behavior but with signs of superconductivity. We measured the magnetoresistance (MR) of these bilayers versus temperature with and without a magnetic field H normal to the wafer (MR = [R(H) − R(0)]/{[R(H) + R(0)]/2}), and under three electric gate-fields of 0 and ±2 MV/cm. The MR results showed a complex set of gate sensitive peaks which extended up to about 30 K. The results are discussed in terms of vortex physics, and the origin of the different MR peaks is identified and attributed to flux-flow MR in the isolated NbN islands and the different proximity regions in the Bi 2 Se 3 cap-layer. The dominant MR peak was found to be consistent with enhanced proximity induced superconductivity in the topological edge currents regions. The high temperature MR data suggest a possible pseudogap phase or a highly extended fluctuation regime.

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Near-zero-energy end states in topologically trivial spin-orbit coupled superconducting nanowires with a smooth confinement

Cited by 370 publications

References 32 publications

Thermoelectrical detection of Majorana states

Thermoelectrical detection of Majorana states

SNS junctions in nanowires with spin-orbit coupling: Role of confinement and helicity on the subgap spectrum

Magnetoresistance, Gating and Proximity Effects in Ultrathin NbN-Bi2Se3 Bilayers

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