SQUIDs: Principles, Noise, and Applications

Clarke, John

doi:10.1016/b978-0-12-601715-1.50006-6

Cited by 19 publications

(7 citation statements)

References 76 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2. As the figure indicates, the maximum ratchet velocity (5.2 m/s) is high enough to move a vortex across the typical few micrometer wide sample [3] in a few microseconds. Furthermore, increasing the vortex density by two orders of magnitude decreases the vortex velocity only by a factor of three.…”

mentioning

confidence: 96%

“…Once present, vortices dissipate energy and generate internal noise, limiting the operation of numerous superconducting devices [2,3]. Methods used to overcome this difficulty include the pinning of vortices by the incorporation of impurities and defects [4], the construction of flux dams [5], slots and holes [6] and magnetic shields [2,3] which block the penetration of new flux lines in the bulk of the SC or reduce the magnetic field in the immediate vicinity of the superconducting device. Naturally, the most desirable would be to remove the vortices from the bulk of the SC.…”

mentioning

confidence: 99%

“…Furthermore, for superconductors with elliptic cross section the geometric barrier can be eliminated [11], thus phase I with complete vortex removal could be extended to high magnetic fields as well.Vortex removal is important for numerous SC applications and can improve the functioning of several devices. An immediate application of the proposed method would be improving the operation of superconducting quantum interference devices (SQUIDs), used as sensors in a wide assortment of scientific instruments [3,12,13]. A longstanding issue in the performance of SQUIDs is 1/f noise [6,12], arising from the activated hopping of trapped vortices [1].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Reducing vortex density in superconductors using the ‘ratchet effect’

Lee¹,

Jankó²,

Derényi³

et al. 1999

Nature

267

206

View full text Add to dashboard Cite

PACS numbers:A serious obstacle that impedes the application of low and high temperature superconductor (SC) devices is the presence of trapped flux [1,2]. Flux lines or vortices are induced by fields as small as the Earth's magnetic field. Once present, vortices dissipate energy and generate internal noise, limiting the operation of numerous superconducting devices [2,3]. Methods used to overcome this difficulty include the pinning of vortices by the incorporation of impurities and defects [4], the construction of flux dams [5], slots and holes [6] and magnetic shields [2,3] which block the penetration of new flux lines in the bulk of the SC or reduce the magnetic field in the immediate vicinity of the superconducting device. Naturally, the most desirable would be to remove the vortices from the bulk of the SC. There is no known phenomenon, however, that could form the basis for such a process. Here we show that the application of an ac current to a SC that is patterned with an asymmetric pinning potential can induce vortex motion whose direction is determined only by the asymmetry of the pattern. The mechanism responsible for this phenomenon is the so called ratchet effect [7][8][9], and its working principle applies to both low and high temperature SCs. As a first step here we demonstrate that with an appropriate choice of the pinning potential the ratchet effect can be used to remove vortices from low temperature SCs in the parameter range required for various applications.Consider a type II superconductor film of the geometry shown in Fig. 1, placed in an external magnetic field H. The superconductor is patterned with a pinning potential U (x, y) = U (x) which is periodic with period ℓ along the x direction, has an asymmetric shape within one period, and is translationally invariant along the y direction of the sample. The simplest example of an asymmetric periodic potential, obtained for example by varying the sample thickness, is the asymmetric sawtooth potential, shown in Fig. 1b. In the presence of a current with density J flowing along the y axis the vortices move with the velocitywhere f L = (J ×ĥ)Φ 0 d/c is the Lorentz force moving the vortices transverse to the current,ĥ is the unit vector pointing in the direction of the external magnetic field H, f u = − dU dxx is the force generated by the periodic potential, f vv is the repulsive vortex-vortex interaction, Φ 0 = 2.07 × 10 −7 G cm 2 is the flux quantum, η is the viscous drag coefficient, and d is the length of the vortices (i.e. the thickness of the sample).When a dc current flows along the positive y direction, the Lorentz force moves the vortices along the positive x direction with velocity v + . Reversing the current reverses the direction of the vortex velocity, but its magnitude, |v − |, due to the asymmetry of the potential, is different from v + . For the sawtooth potential shown in Fig. 1b the vortex velocity is higher when the vortex is driven to the right, than when it is driven to the left (v + > |v − |). As a consequence the applicati...

show abstract

mentioning

confidence: 96%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Reducing vortex density in superconductors using the ‘ratchet effect’

Lee¹,

Jankó²,

Derényi³

et al. 1999

Nature

267

206

View full text Add to dashboard Cite

show abstract

“…35 Clarke's Czolgosz embodies nineteenth-century working-class anger. Clarke suggests that in the autumn of 1897, Czolgosz had a mental breakdown, following the outbreak of violence at Lattimer Mines, in eastern Pennsylvania, which began on September 10, 1897, and in which sixteen Slavic workers were slaughtered 107 . Czolgosz, Clarke writes, was "obsessed with the need for social change in America" because he knew that the problems of poverty and of crime were "symptoms of political and economic oppression."…”

Section: The Life Of An Unknown Assassin: Leon Czolgosz and The Deathmentioning

confidence: 99%

“…Briggs offers no explanation for Waldeck's portrayal of his brother falling apart. Clarke, however, relies on Waldeck's description and on another quote from Czolgosz to Waldeck, "I can't stand it any longer", to arrive at his diagnosis of a mental breakdown 112 . Clarke, however, splices these two quotes together from Briggs's book, when in fact, according to Briggs, they occurred three years apart.…”

Section: The Life Of An Unknown Assassin: Leon Czolgosz and The Deathmentioning

confidence: 99%

The Life of an Unknown Assassin: Leon Czolgosz and the Death of William McKinley

Federman¹

2010

chs

View full text Add to dashboard Cite

Tunneling and Josephson Junctions

Ruggiero

1999

Wiley Encyclopedia of Electrical and Electronics Engineering

View full text Add to dashboard Cite

The sections in this article are Metal–Insulator–Metal Tunneling Alternating Current Josephson Effect Magnetic‐Field Effects The Resistively Shunted Junction ( RSJ ) Model Superconducting Quantum Interference Devices Mixing and Detection Digital Applications High‐Temperature Superconductor Systems Three‐Terminal Devices Related Superconducting Devices Acknowledgments

show abstract

SQUIDs: Principles, Noise, and Applications

Cited by 19 publications

References 76 publications

Reducing vortex density in superconductors using the ‘ratchet effect’

Reducing vortex density in superconductors using the ‘ratchet effect’

The Life of an Unknown Assassin: Leon Czolgosz and the Death of William McKinley

Tunneling and Josephson Junctions

Contact Info

Product

Resources

About