Stable 1 volt programmable voltage standard

Benz, Samuel P.; Hamilton, C.A.; Burroughs, Charles J.; Harvey, Todd E.; Christian, L.A.

doi:10.1063/1.120189

Cited by 162 publications

(73 citation statements)

References 6 publications

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“…We have clarified the mechanism of stimulated superconductivity, shown how the supercurrent depends on the field strength non-monotonically, and predicted the modification of the current-phase relation. Moreover, our results pave the way for filling some remaining gaps in the understanding of SNS junction physics such as the finite-voltage Shapiro steps [12] or the role of phase fluctuations providing the "intrinsic shunting" [23].…”

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confidence: 99%

Theory of Microwave-Assisted Supercurrent in Diffusive SNS Junctions

et al. 2010

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The observation of very large microwave-enhanced critical currents in superconductor-normal metal-superconductor (SNS) junctions at temperatures well below the critical temperature of the electrodes has remained without a satisfactory theoretical explanation for more than three decades. Here we present a theory of the supercurrent in diffusive SNS junctions under microwave irradiation based on the quasiclassical Green's function formalism. We show that the enhancement of the critical current is due to the energy redistribution of the quasiparticles in the normal wire induced by the electromagnetic field. The theory provides predictions across a wide range of temperatures, frequencies, and radiation powers, both for the critical current and the current-phase relationship.It was predicted by Eliashberg already in 1970 [1] that the condensation energy of a superconducting thin film can be increased by irradiating the film with microwaves. Within the framework of his theory, one can explain the microwave-induced increase of the critical current of superconducting bridges for temperatures very close to the critical temperature [2][3][4], which is known as the DayemWyatt effect. However, Eliashberg's mechanism fails to explain a related effect in diffusive SNS junctions. Several experiments have shown that upon irradiation the critical current can be enhanced by up to several orders of magnitude, even at temperatures well below the critical temperature of the superconducting electrodes [5,6]. Additionally, these experiments show that the critical current is a nonlinear function of the radiation power, which existing linear response theories [7,8] cannot explain.There is now renewed interest in this problem, triggered by recent experiments. Fuechsle et al. [9] measured the current-phase relationship under microwave irradiation, and reported that the current is progressively suppressed at phase differences close to π as the radiation amplitude increases. Moreover, Chiodi et al. [10] observed that critical current is enhanced when the microwave frequency is larger than the inverse diffusion time in the normal metal.To understand the microwave-assisted supercurrent in diffusive SNS junctions, we develop a microscopic theory based on the quasiclassical Keldysh-Usadel approach, which takes into account the nonlinear effects of the microwave irradiation. Our theory provides a quantitative description for a wide range of values of the temperature, microwave power, frequency, and the strength of inelastic scattering. In particular, we show that the large enhancement of the critical current originates from the presence of a minigap, E g , in the density of states of the normal wire. This minigap blocks some of the transitions caused by the microwave radiation, which results in a redistribution of quasiparticles, enhancing the supercurrent when the temperature T is comparable or larger than E g /k B . We also show that the nonequilibrium distribution in the normal wire leads to a highly non-sinusoidal currentphase relationship, ...

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confidence: 99%

Theory of Microwave-Assisted Supercurrent in Diffusive SNS Junctions

et al. 2010

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“…A 2.5 V primary voltage system based on a NISTfabricated programmable array of Josephson junctions and developed electronics 40,41 is used as the programmable Josephson voltage standard (PJVS). 42 The leakage resistance FIG. 7.…”

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Invited Article: A precise instrument to determine the Planck constant, and the future kilogram

Haddad

Seifert

Chao

et al. 2016

Review of Scientific Instruments

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A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck constant is established by the practical realization of the electrical units derived from the Josephson and the quantum Hall effects. We describe in this paper the fourth-generation watt balance at the National Institute of Standards and Technology (NIST), and report our initial determination of the Planck constant obtained from data taken in late 2015 and the beginning of 2016. A comprehensive analysis of the data and the associated uncertainties led to the SI value of the Planck constant, h = 6.626 069 83(22) × 10−34 J s. The relative standard uncertainty associated with this result is 34 × 10−9.

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“…Large and reproducible arrays have been fabricated either by using very small area (close to 1 ) SNS junctions with PdAu or MoSi metallic barriers, which give high current steps [2], [3], or by externally shunted SIS and SINIS junctions with moderately large dimensions and reduced critical currents [4]. Also superconductor-correlated metal-superconductor junctions have been proposed, to obtain large characteristic voltage [5].…”

Section: Introductionmentioning

confidence: 99%

RF Properties of Overdamped SIS Junctions

Lacquaniti

Cagliero

Maggi

et al. 2005

IEEE Trans. Appl. Supercond.

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A new type of nonhysteretic Josephson junction suitable for applications in voltage metrology has been developed. These junctions derive from the Nb Al AlO Nb SIS junctions using a relatively thick Al layer oxidized at a low value of oxygen exposure. This produces junctions with reproducible and spatially homogeneous -characteristics, having current densities ranging from 10 3 to more than 2 10 4 A cm 2 and characteristic voltages up to 0.40 mV. The authors report here the rf response of these junctions at 70 GHz. The authors have measured the dependence of the rf-induced steps on the microwave power and the stability of the steps, in view of a future application of these junctions to an ac Josephson voltage standard.

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Stable 1 volt programmable voltage standard

Cited by 162 publications

References 6 publications

Theory of Microwave-Assisted Supercurrent in Diffusive SNS Junctions

Theory of Microwave-Assisted Supercurrent in Diffusive SNS Junctions

Invited Article: A precise instrument to determine the Planck constant, and the future kilogram

RF Properties of Overdamped SIS Junctions

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