Epitaxy of semiconductor–superconductor nanowires

Krogstrup, Peter; Ziino, N. L. B.; Chang, Won; Albrecht, S. M.; Madsen, Morten Hannibal; Johnson, Erik; Nygård, Jesper; Marcus, C. M.; Jespersen, Thomas Sand

doi:10.1038/nmat4176

Cited by 491 publications

(638 citation statements)

References 32 publications

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“…The important universal feature is that the dephasing rate exhibits some characteristic dependence on the typical fluctuation amplitude for the σ z coupling in Eq. (25); that alone is sufficient to link ω 0 and T 2 via a scaling relation akin to Eq. (31).…”

Section: Dephasing Time Tmentioning

confidence: 99%

“…(25). If one initializes the system into, say, the j0i logical qubit state (which is split from the j1i state by a finite energy ℏω 0 ) via the manipulations in the top two panels of Fig.…”

Section: Relaxation Time Tmentioning

confidence: 99%

“…[23]). In parallel, fabrication advances [24,25] have improved device quality, leading to cleaner transport characteristics [26] as well as surprisingly long quasiparticle poisoning times in proximitized nanowires [27] and related setups [28]. Branched wires, another key ingredient toward Majorana networks [29][30][31][32][33][34][35], have also been realized and investigated recently [36].…”

Section: Introductionmentioning

confidence: 99%

“…First, we continue to use the twolevel qubit Hamiltonian in Eq. (25) to treat fluctuations that produce relaxation. Thus, we incorporate only classical noise.…”

mentioning

confidence: 99%

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Milestones Toward Majorana-Based Quantum Computing

et al. 2016

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We introduce a scheme for preparation, manipulation, and read out of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. We outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current, (2) validation of a prototype topological qubit, and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The first two milestones require only a single wire with two islands, and additionally enable sensitive measurements of the system's excitation gap, quasiparticle poisoning rates, residual Majorana zero-mode splittings, and topological-qubit coherence times. These pre-braiding experiments can be adapted to other manipulation and read out schemes as well.

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Section: Dephasing Time Tmentioning

confidence: 99%

Section: Relaxation Time Tmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…First, we continue to use the twolevel qubit Hamiltonian in Eq. (25) to treat fluctuations that produce relaxation. Thus, we incorporate only classical noise.…”

mentioning

confidence: 99%

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Milestones Toward Majorana-Based Quantum Computing

et al. 2016

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“…[9][10] In addition, the mobility in nanowires can be strongly impacted by adsorbates on the uncontacted area. 15 A recent advance in nanowire synthesis has produced epitaxy of superconducting aluminum to InAs nanowires, [16][17] but residual disorder in the InAs nanowire results in unintentional quantum confined regions in these wires. 17 InSb NWs, in contrast, have higher electron mobility 9,15,18 and, as evidenced by clear demonstrations of quantized conductance, 10,19 less intrinsic disorder than InAs NWs.…”

Section: Mainmentioning

confidence: 99%

Hybrid superconductor-quantum point contact devices using InSb nanowires

Gill

Damasco

Car

et al. 2016

Applied Physics Letters

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Proposals for studying topological superconductivity and Majorana bound states in nanowires proximity coupled to superconductors require that transport in the nanowire is ballistic. Previous work on hybrid nanowire-superconductor systems has shown evidence for Majorana bound states, but these experiments were also marked by disorder, which disrupts ballistic transport. In this letter, we demonstrate ballistic transport in InSb nanowires interfaced directly with superconducting Al by observing quantized conductance at zero-magnetic field. Additionally, we demonstrate that the nanowire is proximity coupled to the superconducting contacts by observing Andreev reflection. These results are important steps for robustly establishing topological superconductivity in InSb nanowires. MainInAs and InSb nanowires (NWs) coupled to superconductors are promising material candidates for studying topological superconductivity harboring Majorana bound states 1,2 and demonstrating non-Abelian particle statistics relevant for topological quantum computation. 3 The basic procedure to observe Majorana zero modes involves tuning a superconducting proximity coupled quantum wire (i.e. a ballistic 1D system) with strong spin-orbit coupling and one spin degenerate mode in magnetic field. 1 Indeed, evidence for Majorana bound states has been observed in proximity-coupled InSb and InAs NWs as a zero-bias conduction peak in tunneling experiments. 4-7 However, preliminary experiments probing Majorana bound states in nanowires were marked by disorder and a soft superconducting gap in the tunneling regime. [4][5][6][7][8] Disorder in nanowire systems is known to break up ballistic transport 9,10 , which is a crucial ingredient for developing 1D topological superconductivity. 1, 2, 4, 9 Additionally, disorder can produce zero-bias conductance signatures similar to Majorana bound states. 11 While the typical signature of ballistic 1D transport-quantized conductance-has been observed in InSb nanowires at high magnetic field 9 and more recently at zero-field, 19 clear demonstrations of ballistic transport at lower fields (< 1T, i.e., before the expected onset of topological superconductivity) in hybrid nanowire-superconductor systems are lacking. Hence, in order to clearly demonstrate topological superconductivity and remove alternative 2 mechanisms for observing zero bias conduction peaks, quantized conductance should be observed at zero magnetic field in NWs proximity coupled to superconductors.Quantized conductance at zero-magnetic field is the step-like increase of conductance with gate voltage through a ballistic 1D constriction, in units of the quantum of conductance, G 0 = 2e 2 /h, for each spin degenerate subband. 12 While quantized conductance in QPCs defined on 2D electron gas (2DEG) materials, such as GaAs heterostructures, is well established, 12-14 demonstrations of quantized conductance in nanowire systems are sparse. In contrast to QPCs in 2DEGs, short nanowire channels contacted by metals are more prone to backscattering ef...

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I n A s1‐x S bx / A l core‐shell nanowire epitaxy

Kanne

Gejl

Sestoft

et al. 2016

European Microscopy Congress 2016: Proceedings

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Hybrid materials with topological classification have received immense attention in recent years and become a focal point of condensed‐matter research [1‐2]. This development is to a large extent driven by the search for materials hosting Majorana bound states, proposed as building blocks for topologically protected quantum computation [3]. Recently, semi‐ and superconducting hybrid nanowires (NW) have been shown to be a feasible material combination, fulfilling the criteria of withstanding high magnetic fields while maintaining large spin‐orbit interaction of the semiconductors [4]. Prior growth studies of semiconducting InAs NWs with epitaxial superconducting Al shells have given detailed insight into the mechanisms of Al grain growth kinetics and especially how the growth evolution depends on the NW morphology [5]. In general, the quality of the interfaces have been shown to play an essential role in a variety of nanostructured device applications, ranging from photovoltaics to quantum transport, and is therefore an important hybrid material characteristics. In this study we present compositional and structural control of InAs 1‐x Sb x NWs grown by molecular beam epitaxy (MBE), ranging from pure InAs to pure InSb. We show that the hybrid system, InAs 1‐x Sb x with epitaxial Al, offers new possibilities to form alternative epitaxially matched interfacial domains controlled by the Sb influence on the lattice parameter and the broken bond energy of the facets. By changing the molar fraction of Sb, the electrical properties of the semiconducting core can be tuned to desirable properties, which may be relevant for designing topological superconducting materials. An example of the InAs 1‐x Sb x /Al hybrid system is shown in figure 1 with x = 0.34. Also presented in this study is a method to grow long and pure wurtzite (WZ) InAs 1‐x Sb x NWs having a surprisingly high degree of epitaxial match between Al and the NWs.

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Epitaxy of semiconductor–superconductor nanowires

Cited by 491 publications

References 32 publications

Milestones Toward Majorana-Based Quantum Computing

Milestones Toward Majorana-Based Quantum Computing

Hybrid superconductor-quantum point contact devices using InSb nanowires

I n A s1‐x S bx / A l core‐shell nanowire epitaxy

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