Vortex unbinding and layer decoupling in epitaxial<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Bi</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:ma

Miu, L.; Wagner, Patrick; Frey, Urban; Hadish, A.; Miu, Dana; Adrian, H.

doi:10.1103/physrevb.52.4553

Cited by 37 publications

(16 citation statements)

References 37 publications

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“…For comparison, at 1 T, UӍ2ϫ10 4 -4ϫ10 4 K, 500-1500 K, and 1300-2000 K for YBCO and BSCCO 2212 and BSCCO 2223, respectively. 2,[19][20][21][22] Another interesting parameter is the irreversibility field H irr , namely the field which corresponds to the onset of dissipation ͓in our case the field such that (H irr ,T)/(0,300 K)ϭ10 Ϫ4 ͔. For the 5ϫ2 superlattices 0 H irr was found to be 1 T, for a reduced temperature T/T c …”

Section: Rapid Communicationsmentioning

confidence: 98%

“…In comparison ␥ is equal to 5 for YBCO, and 60-900, 30-300 ͑depending on the oxide content in the Bi-O layers͒ for BSCCO 2212 and for BSCCO 2223, respectively. 4,[20][21][22] The approach proposed in this communication presents an element of novelty relative to the experiments carried out in the past on YBCO/PrBCO artificial structures. Namely, both YBCO and PrBCO unit cells individually contain a CR block together with an IL block, in which the PrBCO layer is nonsuperconducting, probably due to charge compensation.…”

Section: Rapid Communicationsmentioning

confidence: 98%

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Interlayer coupling in ultrathin high-Tcartificial structures

Balestrino¹,

Lavanga²,

Medaglia³

et al. 2001

Phys. Rev. B

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Artificially layered superlattices were grown, by stacking in sequence ultrathin epitaxial layers of (Ba 0.9 , Nd 0.1 )CuO 2ϩx and CaCuO 2 . Starting from ͓(Ba 0.9 , Nd 0.1 )CuO 2ϩx ͔ m /͓CaCuO 2 ͔ 2 superlattices with m ϭ2, the thickness of the Ba-Cu-O block, separating adjacent Ca-Cu-O superconducting blocks, was gradually increased up to mϭ10. We found that, increasing m, superlattices show a moderate decrease of the critical temperature and a sizeable increase of the anisotropy. In the superlattices with mу4 the superconducting layers are completely decoupled, showing, relative to the mϭ2 superlattice, a decrease of the transition temperature less than 10% and an increase of the anisotropy by a factor ϳ2-3. Superconductivity at 55 K was found in ultrathin films only consisting of one (CaCuO 2 ͒ 2 layer sandwiched between five (Ba 0.9 , Nd 0.1 ͒CuO 2ϩx layers, demonstrating that the interlayer coupling in mу4 superlattices is negligible.High-temperature superconducting materials ͑HTSC͒ have a layered structure ͑''natural'' superlattices͒ consisting of two different blocks, with different functional properties, regularly stacked along the c-axis, named the ''infinite layer'' ͑IL͒ block and the ''charge reservoir'' ͑CR͒ block. The IL block consists of N ͑with 1рNр4͒ CuO 2 planes ͑considered essential for high temperature superconductivity͒ separated mostly by alkaline earth. 1 The composition and crystallographic structure of the CR blocks vary from compound to compound. It is commonly accepted that the role of the CR block, in HTSC materials, is to furnish extra chargecarriers to the otherwise insulating IL block.Due to the extremely short coherence length along the c axis, adjacent IL conducting blocks are only weakly coupled, so that HTSC materials show a quasi two-dimensional ͑2D͒ character in a large number of their physical properties. 2 The zero-temperature coherence length of YBa 2 Cu 3 O 7Ϫ␦ ͑YBCO͒, for instance, is 2-3 Å along the c axis ͑Ӎ15 Å in the a-b plane͒, much shorter than the c-axis lattice parameter ͑Ӎ12 Å͒. 3 Nevertheless, YBCO behaves as a threedimensional anisotropic superconductor, at least near T c . On the other hand, the Bi 2 Sr 2 Ca NϪ1 Cu N O 2Nϩ4ϩ␦ ͓BSCCO 22(NϪ1)N͔ compounds, where adjacent conducting blocks, containing N superconducting CuO 2 planes, are separated by two Bi-O layers, are found to be much more anisotropic than the YBCO compound, showing nearly two-dimensional behavior in many physical properties. 4 Although all HTSC materials are strongly anisotropic, the question of the necessity of coupling ͑even very weak͒ between neighboring conducting blocks for the superconducting properties is still open.In the past, several experiments have been carried out on ultrathin superconducting YBCO layers ͓always sandwiched between thick nonsuperconducting PrBa 2 Cu 3 O 7 ͑PrBCO͒ layers͔, on one-half unit cell thick BSCCO 2212, and on ͑YBCO͒/͑PrBCO͒ superlattices in which the thickness of the PrBCO barrier layer, deposited in order to separate successive ultrathin YBCO layers, was c...

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Section: Rapid Communicationsmentioning

confidence: 98%

Section: Rapid Communicationsmentioning

confidence: 98%

Interlayer coupling in ultrathin high-Tcartificial structures

Balestrino¹,

Lavanga²,

Medaglia³

et al. 2001

Phys. Rev. B

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“…11,12 At first sight, this would be in conflict with the form of the I-V curves below the resistive transition reported in Ref. 8, which indicates the existence of a finite critical-current density. The often reported 2D behavior above the resistive transition of HTSC's can be the result of the occurrence of a vortex-fluctuation-induced layer decoupling, as predicted by Monte Carlo simulations 13,14 and recent renormalizationgroup analyses.…”

Section: Introductionmentioning

confidence: 51%

“…The large intrinsic anisotropy, as in the case of Bi 2 Sr 2 CaCu 2 O 8ϩ␦ ͑Bi-2212͒ HTSC, generated by the layered structure, suggests that the thermally excited 2D vortices of opposite helicity in the superconducting Cu-O layers play the essential role. 1 Some transport measurements 2 signaled features of the Berezinskii-Kosterlitz-Thouless ͑BKT͒ transition 3,4 at the superconducting layer level, but the nonvanishing interlayer Josephson coupling gives rise to a finite critical-current density, [5][6][7][8] and the picture becomes complex.…”

Section: Introductionmentioning

confidence: 99%

Length-scale-dependent vortex-antivortex unbinding in epitaxialBi2Sr2CaCu
Miu
¹
,
Jakob
²
,
Haibach
³

et al. 1998
Phys. Rev. B
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0
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The supercurrent transport properties of epitaxial Bi 2 Sr 2 CaCu 2 O 8ϩ␦ films in zero applied magnetic field were investigated in a temperature interval of Ϸ20 K below the mean-field critical temperature T c0 . The modification of the shape of the I-V curves observed by varying the temperature was explained in terms of vortexfluctuation-induced layer decoupling and vortex-antivortex unbinding, revealing a strong probing-length dependence. The change of the effective dimensionality of thermally excited vortices involved in the dissipation process leads to the appearance of a few characteristic regions in the current-temperature diagram. Above a temperature value T*ϽT c0 , the superconducting layers are decoupled, as predicted by Monte Carlo simulations and renormalization-group analyses. In this region, the resistivity exhibits two-dimensional ͑2D͒ behavior corresponding to the superconducting ͑CuO 2 ) 2 layers ͑2D-layer behavior͒. However, the resistive transition seems to be mainly related to the 2D behavior at the film level. In the sensitivity window of our measurements, finite resistance in the limit of small transport currents was detected to occur above a temperature value T c ϽT*, through the dissociation of vortex-string-antivortex-string pairs. By decreasing the temperature and/or by increasing the transport current, the I-V curves in the double logarithmic plot show a clear downward curvature. This can be described in terms of current-induced quasi-2D vortex pair unbinding, with a nonzero critical-current density resulting from the interlayer Josephson coupling. At even lower temperatures and/or higher transport currents, the I-V curves exhibit a crossover from quasi-2D to 2D-layer behavior, due to the decrease of the probing length below the Josephson length, where the interlayer Josephson coupling becomes irrelevant. The temperature dependence of the 2D I-V exponent is in good agreement with recent Langevin simulations of the Coulomb gas model, revealing an anomalous diffusion of vortex fluctuations.

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“…The best available long length monocore tapes have critical current density (77 K, 0 T) kA/cm , but there is increasing evidence that this is by no means the ultimate limiting value [2], [3]. For example, (77 K, 0 T) as high as 70 kA/cm has been achieved for short multifilament samples [4].…”

Section: Introductionmentioning

confidence: 99%

Local measurement of current density by magneto-optical current reconstruction in normally and overpressure processed Bi-2223 tapes

Patnaik

Feldmann

Polyanskii

et al. 2003

IEEE Trans. Appl. Supercond.

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Abstract-Magneto-optical current reconstruction has been used for detailed analysis of the local critical current density ( ) variation in monocore Bi-2223 tapes. We find, even in high quality tapes with bulk transport 40 kA/cm 2 (77 K, 0 T), that there exist local regions which possess current densities of more than 200 kA/cm 2 . Overpressure processing at 148 bar significantly improved to 48 kA/cm 2 by improving the connectivity. For the overpressure-processed sample we find that the current distribution is more uniform and that the maximum local current density at 77 K is increased almost to 300 kA/cm 2 .

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Vortex unbinding and layer decoupling in epitaxialBi2Sr2

Cited by 37 publications

References 37 publications

Interlayer coupling in ultrathin high-Tcartificial structures

Interlayer coupling in ultrathin high-Tcartificial structures

Length-scale-dependent vortex-antivortex unbinding in epitaxialBi2Sr2CaCu
Miu
¹
,
Jakob
²
,
Haibach
³

et al. 1998
Phys. Rev. B
Self Cite
13
0
6
0
View full text Add to dashboard Cite

Local measurement of current density by magneto-optical current reconstruction in normally and overpressure processed Bi-2223 tapes

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Vortex unbinding and layer decoupling in epitaxialBi2Sr2

Cited by 37 publications

References 37 publications

Interlayer coupling in ultrathin high-Tcartificial structures

Interlayer coupling in ultrathin high-Tcartificial structures

Length-scale-dependent vortex-antivortex unbinding in epitaxialBi2Sr2CaCuMiu1, Jakob2, Haibach3 et al. 1998Phys. Rev. BSelf Cite13060View full textAdd to dashboardCite

Local measurement of current density by magneto-optical current reconstruction in normally and overpressure processed Bi-2223 tapes

Contact Info

Product

Resources

About

Length-scale-dependent vortex-antivortex unbinding in epitaxialBi2Sr2CaCu
Miu
¹
,
Jakob
²
,
Haibach
³

et al. 1998
Phys. Rev. B
Self Cite
13
0
6
0
View full text Add to dashboard Cite