From InSb Nanowires to Nanocubes: Looking for the Sweet Spot

Plissard, Sébastien; Slapak, Dorris R.; Verheijen, Marcel A.; Hocevar, Moïra; Immink, George; Weperen, Ilse van; Nadj-Perge, Stevan; Frolov, Sergey; Kouwenhoven, Leo P.; Bakkers, Erik P. A. M.

doi:10.1021/nl203846g

Cited by 118 publications

(177 citation statements)

References 31 publications

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“…To make the devices, we use InSb nanowires (1-3 µm long, 50-80 nm diameter) grown by metal-organic phase epitaxy, 18 which are then transferred from the growth chip by use of a micromanipulator to a pre-patterned Si chip with a 300 nm silicon dioxide layer serving as a gate dielectric. The chip is cleaned using reactive ion etching prior to nanowire deposition to remove resist polymers that can degrade nanowire transport.…”

Section: Mainmentioning

confidence: 99%

“…Previous characterization of similarly grown InSb nanowires provided an extracted mean free path of 300 nm. 9,18 The contact spacing for the InSb nanowire/superconductor QPCs is L=150-300 nm, so the channel length is comparable to or smaller than the mean free path of the nanowire. Nanowire devices are wirebonded immediately after liftoff and left in vacuum (≤10 -2 mBar) for 24-48 hours to remove adsorbates before measurement in a dilution fridge.…”

Section: Mainmentioning

confidence: 99%

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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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Section: Mainmentioning

confidence: 99%

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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“…We continue with the experiment. InSb nanowires [35] with diameter W ≈ 100 nm are deposited onto a substrate with a global back gate. A large ( 2 μm) contact separation ensures sufficient scattering between the source and drain.…”

mentioning

confidence: 99%

Spin-orbit interaction in InSb nanowires

et al. 2015

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We use magnetoconductance measurements in dual-gated InSb nanowire devices, together with a theoretical analysis of weak antilocalization, to accurately extract spin-orbit strength. In particular, we show that magnetoconductance in our three-dimensional wires is very different compared to wires in two-dimensional electron gases. We obtain a large Rashba spin-orbit strength of 0.5-1 eVÅ corresponding to a spin-orbit energy of 0.25-1 meV. These values underline the potential of InSb nanowires in the study of Majorana fermions in hybrid semiconductor-superconductor devices. Hybrid semiconductor nanowire-superconductor devices are a promising platform for the study of topological superconductivity [1]. Such devices can host Majorana fermions [2,3], bound states with non-Abelian exchange statistics. The realization of a stable topological state requires an energy gap that exceeds the temperature at which experiments are performed (∼50 mK). The strength of the spin-orbit interaction (SOI) is the main parameter that determines the size of this topological gap [4] and thus the potential of these devices for the study of Majorana fermions. The identification of nanowire devices with a strong SOI is therefore essential. This entails both performing measurements on a suitable material and device geometry as well as establishing theory to extract the SOI strength.InSb nanowires are a natural candidate to create devices with a strong SOI, since bulk InSb has a strong SOI [5,6]. Nanowires have been used in several experiments that showed the first signatures of Majorana fermions [7][8][9][10]. Nanowires are either fabricated by etching out wires in planar heterostructures or are grown bottom up. The strong confinement in the growth direction makes etched wires two dimensional (2D) even at high density. SOI has been studied in 2D InSb wires [11] and in planar InSb heterostructures [12], from which a SOI due to structural inversion asymmetry [13], a Rashba SOI α R of 0.03 eVÅ has been obtained [12]. Bottom-up grown nanowires are three dimensional (3D) when the Fermi wavelength is smaller than the wire diameter. In InSb wires of this type, SOI has been studied by performing spectroscopy on quantum dots [14,15] [19,20]. Our approach is to use a high-k dielectric in combination with a top gate that covers the InSb nanowire. The standard method to extract SOI strength in extended regions is through low-field magnetoconductance (MC) measurements [21,22]. Quantum interference (see Fig. 1) in the presence of a strong SOI results in an increased conductance, called weak antilocalization (WAL) [23], that reduces to its classical value when a magnetic field is applied [24]. From fits of MC data to theory a spin relaxation length is extracted. If spin relaxation results from inversion asymmetry, a spin precession length and SOI strength can be defined. To extract SOI strength in nanowires the theory should contain (1) the length over which the electron dephases in the presence of a magnetic field, the magnetic dephasing length [25], and (...

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“…34 Strong spin-orbit interaction has already been established in this material in spin-orbit qubit experiments. 72 , 73 The highest electron mobility among nanowires was measured in InSb nanowires; this offered another advantage, as disorder could lead to the creation of additional Majorana pairs along the nanowire due to fl uctuations in the chemical potential.…”

Section: Topological Qubits and Majorana Fermionsmentioning

confidence: 98%

“…The nanowire density on the substrate is controlled by defi ning arrays of catalyst particles using electron beam lithography. By optimizing the density and growth conditions, such as the temperature and III/V precursor ratio, it is possible to increase the aspect ratio (length/ diameter) of the nanowires up to 35; the longest InSb wires have lengths of up to 4 μ m. 34 New ways to tailor electronic properties, such as crystal structure 35 and strain, 36 have recently been revealed. With nanowires, it is possible to fabricate common semiconductors with a different crystal structure than in bulk.…”

Section: Nanowire Growth and Electrical Propertiesmentioning

confidence: 99%

Quantum computing based on semiconductor nanowires

et al. 2013

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A quantum computer will have computational power beyond that of conventional computers, which can be exploited for solving important and complex problems, such as predicting the conformations of large biological molecules. Materials play a major role in this emerging technology, as they can enable sophisticated operations, such as control over single degrees of freedom and their quantum states, as well as preservation and coherent transfer of these states between distant nodes. Here we assess the potential of semiconductor nanowires grown from the bottom-up as a materials platform for a quantum computer. We review recent experiments in which small bandgap nanowires are used to manipulate single spins in quantum dots and experiments on Majorana fermions, which are quasiparticles relevant for topological quantum computing.

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From InSb Nanowires to Nanocubes: Looking for the Sweet Spot

Cited by 118 publications

References 31 publications

Hybrid superconductor-quantum point contact devices using InSb nanowires

Hybrid superconductor-quantum point contact devices using InSb nanowires

Spin-orbit interaction in InSb nanowires

Quantum computing based on semiconductor nanowires

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