Vortex pinning by disordered columnar defects in large Josephson junctions

Itzler, M. A.; Tinkham, M.

doi:10.1103/physrevb.53.r11949

Cited by 12 publications

(17 citation statements)

References 19 publications

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“…Role of bulk pinning in large Josephson junction (where either the length or width of the junction is larger than the Josephson penetration depth k J has been studied for dierent types of defects (periodic or random with varying sizes) by Fehrenbacher et al [8] through exact solution of the sine-Gordon equation. Experimentally also, the improvement of the junction critical current at commensurate¯ux concentration has been observed [9,10]. Such observations prompt one to study the¯ux pinning as well as critical current in a disordered junction array.…”

Section: U N C O R R E C T E D P R O O Fmentioning

confidence: 73%

Role of intergranular silver in modulating the aperiodicity in disordered Josephson junction arrays: impact on relaxation of intergranular critical state

Pandey

Bhattacharya

Sharma

2000

Physica C: Superconductivity

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Relaxation of the intergranular critical state has been observed at a very low applied magnetic ®eld (10±50 Oe) over a temperature regime of 20±77 K in bulk polycrystalline YBa 2 Cu 3 O 7Àx (YBCO) and Bi 1X75 Pb 0X35 Sr 2 Ca 2 Cu 3 O 10x (BPSCCO) samples. In such a disordered Josephson junction network, the relaxation is slower than the intragranular relaxation and, hence, it yields higher¯ux pinning energy U 0 than the corresponding intragranular values. Silver addition seems to have given rise to much uniformity in the grain boundary characteristics which results in sharp drop in the¯ux pinning energy since it depends on the variation of the junction coupling energy E J across the network. While U 0 % 0X5 and 0.55 eV for the parent BPSCCO and YBCO samples, respectively, in silver added (10±15 wt.%) samples the corresponding values are $0.15 and $0.27 eV. The distribution functions mU for the¯ux pinning energy and nh for the grain boundary misalignment angle h have been evaluated from the experimentally observed patterns of magnetic relaxation and variation of the grain boundary critical ®elds with temperature. The distribution functions become narrower in the case of silver added samples re¯ecting a reduction in the degree of disorder. The variation of the eective vortex mass m Ã with the variation in the degree of disorder is observed. Considering the width of the superconducting transition DT c as the measure of the degree of disorder (inhomogeneity), it has been shown that the transport critical current density J c follows a relationship J c $ expÀDT c while the pinning energy U $ DT c . These relations may help in devising a suitable strategy for achieving the desired eect: high J c yet slower decay rate, i.e., large U. Ó

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Section: U N C O R R E C T E D P R O O Fmentioning

confidence: 73%

Role of intergranular silver in modulating the aperiodicity in disordered Josephson junction arrays: impact on relaxation of intergranular critical state

Pandey

Bhattacharya

Sharma

2000

Physica C: Superconductivity

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“…For example it gives informations on the quality of the junctions. Recent studies by Itzler and Tinkham examine how defects in the coupling affect this maximum current [14,15]. This is important because high T c superconductors can be described as Josephson junctions where the critical current density is a rapidly varying function of the position, due to grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

Designing arrays of Josephson junctions for specific static responses

Caputo¹,

Loukitch²

2008

Inverse Problems

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We consider the inverse problem of designing an array of superconducting Josephson junctions that has a given maximum static current pattern as function of the applied magnetic field. Such devices are used for magnetometry and as Terahertz oscillators. The model is a 2D semilinear elliptic operator with Neuman boundary conditions so the direct problem is difficult to solve because of the multiplicity of solutions. For an array of small junctions in a passive region, the model can be reduced to a 1D linear partial differential equation with Dirac distribution sine nonlinearities. For small junctions and a symmetric device, the maximum current is the absolute value of a cosine Fourier series whose coefficients (resp. frequencies) are proportional to the areas (resp. the positions) of the junctions. The inverse problem is solved by inverse cosine Fourier transform after choosing the area of the central junction. We show several examples using combinations of simple three junction circuits. These new devices could then be tailored to meet specific applications.

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“…Recently, there have been efforts to explore variations of this system in which patterned defects, of virtually any desired strength and geometry, are added to the junction barrier. [1][2][3][4][5][6][7][8] In the defected regions, the barrier thickness is increased, changing locally the critical current density ͑CCD͒ J c and the magnetic thickness d m of the junction. of the junction.…”

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confidence: 99%

“…In typical experimental realizations, the barrier thickness in the defected regions is made much greater than that in the defect-free regions. 5,8 Since the tunneling current has a strong ͑exponen-tial͒ dependence on the barrier thickness, we may consider that practically J c ϭ0 in the defected regions. 8 This kind of inhomogeneity attracts the magnetic flux entering a junction in an external magnetic field, in the form of Josephson fluxons.…”

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confidence: 99%

“…5,8 Since the tunneling current has a strong ͑exponen-tial͒ dependence on the barrier thickness, we may consider that practically J c ϭ0 in the defected regions. 8 This kind of inhomogeneity attracts the magnetic flux entering a junction in an external magnetic field, in the form of Josephson fluxons. Thus this variety of JJ's offers the possibility of providing a controlled environment for addressing general questions concerning flux pinning.…”

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confidence: 99%

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