Closing of the induced gap in a hybrid superconductor-semiconductor nanowire

Puglia, Denise; Martinez, Emanuel Ricardo Monteiro; Ménard, Gerbold; Pöschl, Andreas; Gronin, Sergei; Gardner, G. C.; Kallaher, R. L.; Manfra, Michael J.; Marcus, C. M.; Higginbotham, Andrew; Casparis, Lucas

doi:10.1103/physrevb.103.235201

Cited by 53 publications

(46 citation statements)

References 38 publications

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“…Experimental non-local conductance measurements for disordered physical systems have signaled a gap-closure signature before the appearance of ZBCPs in the local conductance spectrum [33]. This rules out the connection between gap-closure and ABSs.…”

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confidence: 93%

“…Near-zero energy Andreev bound states (ABSs), often termed as quasi-MZMs, mimic most of the local MZM signatures [23][24][25][26][27], which calls for other methodologies to distinguish between trivial and topological zero-energy modes. Recent proposals have focused on exploiting the non-locality of MZMs via non-local transport measurements on three-terminal normal-topological superconductor-normal (N-TS-N) setups [28][29][30][31][32][33]. These non-local signatures could augment the certainty of MZM detection by gauging the nontrivial correlations in the system.…”

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confidence: 99%

“…Theoretical claims have presented the ability of non-local conductance spectra to detect topological phase transition based on the closing of the bulk gap at the phase transition point [30]. However, experiments present contradicting results [33] with the gap closing well before the topological phase transition point. The object of this Letter is to gauge the effectiveness of non-local conductance spectra itself by considering a three terminal setup based on the archetypical TS, the Kitaev chain, in conjunction with the topological entanglement entropy.…”

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confidence: 99%

“…1(a). The three terminal setup [32,33] consists of a grounded superconductor [40] connected to the chain, and two contacts from which independent voltages (V L , V R ) can be applied. We consider two situations: pristine and disordered, as discussed in previous works [41,42].…”

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confidence: 99%

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Can non-local conductance spectra conclusively signal Majorana zero modes? -- Insights from von Neumann entropy

Kejriwal,

Muralidharan

2021

Preprint

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The topological origin of the zero bias conductance signatures obtained via conductance spectroscopy in topological superconductor hybrid systems is a much contended issue. Recently, nonlocal conductance signatures that exploit the non-locality of the zero modes in three terminal hybrid setups have been proposed as means to ascertain the definitive presence of Majorana modes. The topological entanglement entropy, which is based on the von Neumann entropy, is yet another way to gauge the non-locality in connection with the bulk-boundary correspondence of a topological phase. We show that while both the entanglement entropy and the non-local conductance exhibit a clear topological phase transition signature for long enough pristine nanowires, non-local conductance fails to signal a topological phase transition for shorter disordered wires. While recent experiments have indeed shown premature gap-closure signatures in the non-local conductance spectra, we believe that the entanglement entropy can indeed signal a genuine transition, regardless of the constituent non-idealities in an experimental situation. Our results thereby point toward furthering the development of experimental techniques beyond conductance measurements to achieve a conclusive detection of Majorana zero modes.

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confidence: 93%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Can non-local conductance spectra conclusively signal Majorana zero modes? -- Insights from von Neumann entropy

Kejriwal,

Muralidharan

2021

Preprint

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“…As a consequence, it has been proposed that non-local transport setups can give a much cleaner picture of the nature of subgap states [5][6][7] with a small number of recent experiments already available. 8,9 Candidate systems for Majorana zero modes are not limited to one spatial dimension. In a classic paper, 10 Fu and Kane proposed to realize Majorana zero modes in the center of a vortex in the superconducting order parameter assuming the latter pairs a single-species of two-dimensional Dirac quasiparticles.…”

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confidence: 99%

Identifying Majorana vortex modes via non-local transport

Sbierski,

Geier,

et al. 2021

Preprint

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The combination of two-dimensional Dirac surface states with s-wave superconductivity is expected to generate localized topological Majorana zero modes in vortex cores. Putative experimental signatures of these modes have been reported for heterostructures of proximitized topological insulators, iron-based superconductors or certain transition metal dichalcogenides. Despite these efforts, the Majorana nature of the observed excitation is still under debate. We propose to identify the presence of Majorana vortex modes using a non-local transport measurement protocol originally proposed for one-dimensional settings. In the case of an isolated subgap state, the protocol provides a spatial map of the ratio of local charge-and probability-density which offers a clear distinction between Majorana and ordinary fermionic modes. We show that these distinctive features survive in the experimentally relevant case of hybridizing vortex core modes.

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Spin‐Mixing Enhanced Proximity Effect in Aluminum‐Based Superconductor–Semiconductor Hybrids

et al. 2022

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Narrow-gap semiconductors with a large g-factor and low carrier density (such as InAs and InSb) are most commonly used, either as 1D nanowires [3] or 2D electron gases. [4] The first generation of semiconductor-superconductor hybrids was made using Nb [5] and NbTiN [6] as the superconductor. While these materials offer a large superconducting gap and resilience to high magnetic fields, the hybrids suffered from a finite in-gap conductance (often described as "soft-gap"). In addition, Nb-based hybrids have not been shown to host parity-conserving transport-a key ingredient for the development of topological qubits. [7] These drawbacks remained even after substantial improvements of the fabrication, such as epitaxial growth of the superconductor. [8] In the meantime, aluminum has emerged as the material of choice. Thin shells made of this metal combined with an oxide-free interface result in clean electronic transport. [9,10] This includes suppressed sub-gap tunneling conductance (hard induced gap) and parity-conserving transport, [11] which enables the search for topological superconductivity. For a topological phase to emerge, the minimal condition states that the Zeeman energy V g B Z B

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Closing of the induced gap in a hybrid superconductor-semiconductor nanowire

Cited by 53 publications

References 38 publications

Can non-local conductance spectra conclusively signal Majorana zero modes? -- Insights from von Neumann entropy

Can non-local conductance spectra conclusively signal Majorana zero modes? -- Insights from von Neumann entropy

Identifying Majorana vortex modes via non-local transport

Spin‐Mixing Enhanced Proximity Effect in Aluminum‐Based Superconductor–Semiconductor Hybrids

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