Global phase coherence in two-dimensional granular superconductors

Orr, Brian J.; Jaeger, Heinrich M.; Goldman, A. M.; Kuper, C.G.

doi:10.1103/physrevlett.56.378

Cited by 205 publications

(95 citation statements)

References 13 publications

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“…According to the experiments (Jaeger et al, 1989;Orr et al, 1986) the superconductor-insulator transition is controlled by the resistance of the array only and the critical resistance R c (in the case of granular films) is close to the resistance quantum R 0 ≈ 6.4kΩ. The Coulomb interaction drops out from the result.…”

Section: Mean Field Approximationmentioning

confidence: 99%

“…After the pioneering works (Jaeger et al, 1989Orr et al, 1985Orr et al, , 1986 it became clear that the boundary between the superconducting and insulating states at T = 0 is determined by the normal state conductance of the film rather then by the ratio of the Josephson and Coulomb energies. This fact is illustrated by the experimental resistivity temperature dependencies of samples with different thicknesses shown in Fig.…”

Section: Fig 12mentioning

confidence: 99%

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Granular electronic systems

et al. 2007

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A granular metal is an array of metallic nano-particles imbedded into an insulating matrix. Tuning the intergranular coupling strength a granular system can be transformed into either a good metal or an insulator and, in case of superconducting particles, experience superconductor-insulator transition. The ease of adjusting electronic properties of granular metals makes them most suitable for fundamental studies of disordered solids and assures them a fundamental role for nanotechnological applications. This Review discusses recent important theoretical advances in the study of granular metals, emphasizing on the interplay of disorder, quantum effects, fluctuations and effects of confinement in formation of electronic transport and thermodynamic properties of granular materials.

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Section: Mean Field Approximationmentioning

confidence: 99%

Section: Fig 12mentioning

confidence: 99%

Granular electronic systems

et al. 2007

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“…In those experiments [Orr, et al, 1986], samples with R, > 6 kWl were insulating at low temperature, while those with R, < 6 kW were superconducting. Our data are evidence for the T = 0 phase transition predicted to occur in Josephson junctions as the quasiparticle dissipation increases.…”

Section: 8)mentioning

confidence: 92%

Effect of Leads and Quantum Fluctuations in Small Superconducting Tunnel Junctions

Johnson¹

1990

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“…However, as long as these do not span the film the resistance will be determined by single-particle tunneling. The sheet resistance of the resultant network can be inferred using the following simple argument [22]. Disconnect all of the junctions in the network whose conductance involves single particle tunneling, and then reconnect them one by one in ascending order of resistance.…”

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confidence: 99%

Evidence of spatially inhomogeneous pairing on the insulating side of a disorder-tuned superconductor-insulator transition

2008

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Measurements of transport properties of amorphous insulating InxOy thin films have been interpreted as evidence of the presence of superconducting islands on the insulating side of a disorder-tuned superconductor-insulator transition. Although the films are not granular, the behavior is similar to that observed in granular films. The results support theoretical models in which the destruction of superconductivity by disorder produces spatially inhomogenous pairing with a spectral gap.The interplay between localization and superconductivity can be investigated through studies of disordered superconducting films [1], originally treated by Anderson [2], and Abrikosov and Gor'kov [3], who considered the low-disorder regime. Several approaches have been proposed for strong disorder, including fermionic mean field theories [4,5,6] and theories that focus on the universal critical properties near the superconductor-insulator transition. The latter consider the transition to belong to the dirty boson universality class [7]. When quantum fluctuations are included in fermionic theories for high levels of disorder a spatially inhomogeneous pairing amplitude is found which retains a nonvanishing spectral gap [8]. For sufficiently disordered systems inhomogeneous pairing can also be brought about by thermal fluctuations [9]. A similar inhomogeneous regime has also been considered under the rubric of electronic microemulsions in the context of the metal-insulator transition of two dimensional electron gases [10]. In this letter we provide evidence of a spatially inhomogeneous order parameter on the insulating side of a superconductor-insulator transition driven by structural and/or chemical disorder.Studies of disorder and magnetic field tuned superconductor-insulator transitions have usually been carried out on films that are either amorphous or granular. In the former the disorder is on an atomic scale, and in the latter, on a mesoscopic scale in which case the films consist of metallic grains or clusters connected by tunneling, that are either embedded in an insulating matrix, or on a bare substrate [1]. Amorphous films can be produced when films of metal atoms such as Pb or Bi are grown at liquid helium temperatures on substrates precoated with a wetting layer of amorphous Ge or Sb [11], or by careful vapor deposition of Mo x Ge y , In x O y , or TiN using a variety of techniques.Granular films, are known to develop superconductivity in stages. If the grains are small and weakly connected, the film is an insulator. For grains larger than some characteristic size, and sufficiently close together, "local superconductivity" will develop below some temperature. The opening of a spectral gap in the density of states of the grains [12] results in a relatively sharp upturn in the resistance below this temperature, which is usually close to the transition temperature of the bulk material. For well enough coupled grains, there may be a small drop in resistance at that temperature, followed by this upturn. This is in contra...

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Global phase coherence in two-dimensional granular superconductors

Cited by 205 publications

References 13 publications

Granular electronic systems

Granular electronic systems

Effect of Leads and Quantum Fluctuations in Small Superconducting Tunnel Junctions

Evidence of spatially inhomogeneous pairing on the insulating side of a disorder-tuned superconductor-insulator transition

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