Decays of Majorana or Andreev Oscillations Induced by Steplike Spin-Orbit Coupling

Cao, Zhan; Zhang, Hao; Lü, Haifeng; He, Wan-Xiu; Lu, Hai-Zhou; Xie, Xin

doi:10.1103/physrevlett.122.147701

Cited by 56 publications

(26 citation statements)

References 74 publications

(122 reference statements)

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“…are not fully consistent with a Majorana interpretation. Possible discrepancies are the decreasing amplitude of even-odd peak spacing oscillations with magnetic field [30][31][32][33], as well as the low field at which 1e periodicity appeared, compared to the expected value for the topological transition to occur.…”

Section: Introductionmentioning

confidence: 87%

Full parity phase diagram of a proximitized nanowire island

et al. 2021

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We measure the charge periodicity of Coulomb blockade conductance oscillations of a hybrid InSb-Al island as a function of gate voltage and parallel magnetic field. The periodicity changes from 2e to 1e at a gate-dependent value of the magnetic field, B * , decreasing from a high to a low limit upon increasing the gate voltage. In the gate voltage region between the two limits, which our numerical simulations indicate to be the most promising for locating Majorana zero modes, we observe correlated oscillations of peak spacings and heights. For positive gate voltages, the 2e-1e transition with low B * is due to the presence of nontopological states whose energy quickly disperses below the charging energy due to the orbital effect of the magnetic field. Our measurements highlight the importance of a careful exploration of the entire available phase space of a proximitized nanowire as a prerequisite to define future topological qubits.

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Section: Introductionmentioning

confidence: 87%

Full parity phase diagram of a proximitized nanowire island

et al. 2021

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“…The oscillating peak spacing could be attributed to overlapping Majorana wavefunctions 36 . We note that a trivial explanation for the 2e-1e transition based on Andreev bound states cannot be ruled out at this point [37][38][39] .…”

Section: Resultsmentioning

confidence: 74%

“…[36] We note that a trivial explanation for the 2e to 1e transition based on Andreev bound states cannot be ruled out at this point. [37][38][39] We have studied the growth dynamics of in-plane InSb nanowires on InP (111)B substrates. Despite the large mismatch between the wires and the substrate, defect-free single crystalline network channels are formed due to immediate strain-relaxation at the nanowire-…”

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confidence: 99%

In-plane selective area InSb–Al nanowire quantum networks

Veld

Schaller

et al. 2020

Commun Phys

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Strong spin-orbit semiconductor nanowires coupled to a superconductor are predicted to host Majorana zero modes. Exchange (braiding) operations of Majorana modes form the logical gates of a topological quantum computer and require a network of nanowires. Here, we utilize an in-plane selective area growth technique for InSb-Al semiconductor-superconductor nanowire networks. Transport channels, free from extended defects, in InSb nanowire networks are realized on insulating, but heavily mismatched InP (111)B substrates by full relaxation of the lattice mismatch at the nanowire/substrate interface and nucleation of a complete network from a single nucleation site by optimizing the surface diffusion length of the adatoms. Essential quantum transport phenomena for topological quantum computing are demonstrated in these structures including phase-coherence lengths exceeding several micrometers with Aharonov-Bohm oscillations up to five harmonics and a hard superconducting gap accompanied by 2e-periodic Coulomb oscillations with an Al-based Cooper pair island integrated in the nanowire network.

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“…Inhomogeneous potentials naturally arise also in ultracold-atom setups due to the presence of the optical-trap used to confine the atomic cloud [42][43][44][45]. Indeed, trivial ABS may exhibit quantized ZBCP virtually indistinguishable from those produced by MBS [82-84, 86, 88, 93, 95, 101, 102, 105, 107], mimic the oscillations of the energy splitting of MBS in some regimes [106,112], be robust against local perturbations [94,98], and even exhibit nonabelian braiding statistics [97,113]. However, whereas MBS are exponentially localized at the edges of the nanowire or, equivalently, at a topological domain wall, ABS are localized anywhere inside the wire, typically near inhomogeneities or impurities, and do not necessarily exhibit exponential localization [88,[94][95][96]98].…”

Section: Introductionmentioning

confidence: 99%

Majorana/Andreev crossover and the fate of the topological phase transition in inhomogeneous nanowires

Marra,

Nigro

2021

Preprint

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Majorana bound states (MBS) and Andreev bound states (ABS) in realistic Majorana nanowires setups have similar experimental signatures which make them hard to distinguishing one from the other. Here, we characterize the continuous Majorana/Andreev crossover interpolating between fully-separated, partially-separated, and fully-overlapping Majorana modes, in terms of global and local topological invariants, fermion parity, quasiparticle densities, Majorana pseudospin and spin polarizations, density overlaps and transition probabilities between opposite Majorana components. We found that in inhomogeneous wires, the transition between fullyoverlapping trivial ABS and nontrivial MBS does not necessarily mandate the closing of the bulk gap of quasiparticle excitations, but a simple parity crossing of partially-separated Majorana modes (ps-MM) from trivial to nontrivial regimes. We demonstrate that fully-separated and fully-overlapping Majorana modes correspond to the two limiting cases at the opposite sides of a continuous crossover: the only distinction between the two can be obtained by estimating the degree of separations of the Majorana components. This result does not contradict the bulk-edge correspondence: Indeed, the field inhomogeneities driving the Majorana/Andreev crossover have a length scale comparable with the nanowire length, and therefore correspond to a nonlocal perturbation which breaks the topological protection of the MBS.

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Decays of Majorana or Andreev Oscillations Induced by Steplike Spin-Orbit Coupling

Cited by 56 publications

References 74 publications

Full parity phase diagram of a proximitized nanowire island

Full parity phase diagram of a proximitized nanowire island

In-plane selective area InSb–Al nanowire quantum networks

Majorana/Andreev crossover and the fate of the topological phase transition in inhomogeneous nanowires

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