A thin-film cryotron suitable for use as an ultra-low-temperature switch

Lowell, Peter J.; Mates, J. A. B.; Doriese, W. B.; Hilton, G. C.; Morgan, Kelsey M.; Swetz, Daniel S.; Ullom, Joel N.; Schmidt, Daniel R.

doi:10.1063/1.4964345

Cited by 9 publications

(3 citation statements)

References 24 publications

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“…The realization of atomically thin superconductors fosters exciting prospects for materials engineering on the atomistic scale. Notably, they are ideally suited as building blocks for ultrathin and ultra-lightweight cryogenic electronic circuits 31 – 33 where their quasi two-dimensional structure even allows more complex architectures to be constructed as, e.g., van der Waals heterostructures 34 . A limiting factor for these applications is the need for specific intercalants, adatoms or substrates in most current realizations of two-dimensional superconductivity.…”

Section: Introductionmentioning

confidence: 99%

Free surfaces recast superconductivity in few-monolayer MgB2: Combined first-principles and ARPES demonstration

Bekaert

Bignardi

Aperis

et al. 2017

Sci Rep

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Two-dimensional materials are known to harbour properties very different from those of their bulk counterparts. Recent years have seen the rise of atomically thin superconductors, with a caveat that superconductivity is strongly depleted unless enhanced by specific substrates, intercalants or adatoms. Surprisingly, the role in superconductivity of electronic states originating from simple free surfaces of two-dimensional materials has remained elusive to date. Here, based on first-principles calculations, anisotropic Eliashberg theory, and angle-resolved photoemission spectroscopy (ARPES), we show that surface states in few-monolayer MgB2 make a major contribution to the superconducting gap spectrum and density of states, clearly distinct from the widely known, bulk-like σ- and π-gaps. As a proof of principle, we predict and measure the gap opening on the magnesium-based surface band up to a critical temperature as high as ~30 K for merely six monolayers thick MgB2. These findings establish free surfaces as an unavoidable ingredient in understanding and further tailoring of superconductivity in atomically thin materials.

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Section: Introductionmentioning

confidence: 99%

Free surfaces recast superconductivity in few-monolayer MgB2: Combined first-principles and ARPES demonstration

Bekaert

Bignardi

Aperis

et al. 2017

Sci Rep

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show abstract

“…Recently, owing to immense experimental progress 19,20 , superconductivity was realized down to monolayer thickness in several materials -ranging from electronphonon-based superconductors, such as In and Pb 21,22 , NbSe 2 [23][24][25] and doped graphene [26][27][28][29][30][31] , to materials with non-conventional coupling mechanisms, such as La 2−x Sr x CuO 4 32 and FeSe 33 . The promise for extremely low power, ultra-lightweight and ultra-sensitive electronic devices warrants further progress in ultrathin superconductivity [34][35][36] . Quantum confinement in the vertical direction generally separates subbands in ultrathin films, innating multi-band and thereby potentially multi-gap superconductivity 37 .…”

Section: Introductionmentioning

confidence: 99%

Evolution of multigap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB2

Bekaert¹,

Aperis²,

Partoens³

et al. 2017

Phys. Rev. B

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Starting from first principles, we show the formation and evolution of superconducting gaps in MgB2 at its ultrathin limit. Atomically thin MgB2 is distinctly different from bulk MgB2 in that surface states become comparable in electronic density to the bulk-like σ-and π-bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we show that monolayer MgB2 develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film, owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB2 is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to >50 K under biaxial tensile strain of ∼ 4%, which is an enhancement stronger than in any other graphene-related superconductor known to date.

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“…Several groups have demonstrated microwave switches and phase shifters based on Josephson junctions [2][3][4][5][6] , and novel semiconductor devices 1,7 . A cryogenic switch operating at DC, based on a cryotron has also been reported 8 . In this letter, we demonstrate a single pole single throw (SPST) switch fabricated from a nanowire integrated into a superconducting transmission line as an alternative low power, cryogenic microwave switch.…”

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confidence: 99%

Demonstration of a superconducting nanowire microwave switch

Wagner

Ranzani

Ribeill

et al. 2019

Applied Physics Letters

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The functionality of a nanowire integrated into a superconducting transmission line acting as a single pole single throw switch is demonstrated. The switch has an instantaneous bandwidth from 2 to 8 GHz with more than 10 dB of isolation between the open and closed states. The switch consumes no power in the closed state and ≈ 15 nW in the open state. The rise and fall response time between open and closed states is approximately 370 ps. PACS numbers: #Quantum computing architectures employing as many as 72 qubits have recently been demonstrated. In order to scale such architectures further, miniaturized circulators, isolators, and switching networks that have low power consumption while operating at cryogenic temperatures will be necessary 1 . Several groups have demonstrated microwave switches and phase shifters based on Josephson junctions 2-6 , and novel semiconductor devices 1,7 . A cryogenic switch operating at DC, based on a cryotron has also been reported 8 . In this letter, we demonstrate a single pole single throw (SPST) switch fabricated from a nanowire integrated into a superconducting transmission line as an alternative low power, cryogenic microwave switch. Such nanowires are commonly used in the fabrication of superconducting single photon detectors 9-12 , and a three terminal variant of the device has been shown to operate as a transistor for digital logic applications 13 . We present two variants of the switch, one with a single nanowire and a second with two nanowires operated in tandem to provide improved isolation between the open and closed states of the switch. The single nanowire device is a small, w = 80 nm wide nanowire integrated into a superconducting transmission line with two on-chip inductors fabricated in a single metal layer. Surface mount capacitors are soldered off chip onto the transmission line feeding the device, creating a bias tee. Modulation of the switch is achieved by applying a low frequency signal to the inductive ports of the bias tee of sufficient power to exceed the critical current of the nanowire. The switch is in the closed state when the nanowire is superconducting and forms a lossless transmission line. Similarly the switch is open when the nanowire has been driven into the normal state. The switches are fabricated on a single layer of d = 8 nm thick NbN with a sheet resistance of ≈ 356 Ω/square. A wire only 3 squares long fabricated from this material will produce an impedance of ≈ 1 kΩ in the resistive state, enough to obtain more than 20 dB of RF isolation. In the tandem nanowire design a second nanowire increases isolation by shorting one RF port to ground while the first nanowire is simultaneously in the normal state. a) andrew.wagner@raytheon.com V S1 S2 2 µm (a) S1 S2 V 1 V 2 2 µm (b) FIG. 1. SEM micrograph images and circuit diagrams of the single nanowire switch (a) and tandem nanowire switch (b).The single nanowire switch is actuated by a voltage signal V that drives current through a resistor connected to the inductors of the bias tee. The tandem nanow...

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A thin-film cryotron suitable for use as an ultra-low-temperature switch

Cited by 9 publications

References 24 publications

Free surfaces recast superconductivity in few-monolayer MgB2: Combined first-principles and ARPES demonstration

Free surfaces recast superconductivity in few-monolayer MgB2: Combined first-principles and ARPES demonstration

Evolution of multigap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB2

Demonstration of a superconducting nanowire microwave switch

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