Superconductivity in ultrathin artificial cuprate structures

Balestrino, G.; Lavanga, S.; Medaglia, P. G.; Orgiani, P.; Paoletti, A.; Pasquini, G.; Tebano, A.; Tucciarone, A.

doi:10.1063/1.1383270

Cited by 22 publications

(19 citation statements)

References 21 publications

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“…Details of the growth process are reported in Ref. 11. Such heterostructures consist of N CaCuO 2 unit cells, sandwiched between M layers of Ba 0.9 Nd 0.1 CuO 2ϩx ͑namely, the CR block͒.…”

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“…7,8 Following this approach, it has been demonstrated that a single IL block is the minimal structural requirement for high T c superconductivity. [9][10][11] Because of the high oxygen pressure used during film deposition, direct calibration of the deposition rate by monitoring the intensity oscillations of the reflection high-energy electron diffraction ͑RHEED͒ spots is not possible. Precise calibration of the growth rates can be obtained a posteriori by both x-ray diffraction ͑XRD͒ and x-ray reflection ͑XRR͒.…”

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confidence: 99%

“…By alternating the deposition of the ultrathin M /N/M structures with the mϫn superlattices, it was possible to ensure that no changes in the deposition rate occurred. 11 The resistance versus temperature behavior for Nϭ2, 1, and 0.66 was measured and is reported in Fig. 1.…”

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Structural characterization of ultrathin cuprate artificial superconducting structures by x-ray synchrotron radiation

Aruta

Angeloni²,

Balestrino³

et al. 2003

Journal of Applied Physics

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Grazing incidence x-ray diffraction and reflectivity measurements were\ud carried out on ultrathin (a few unit cells thick) superconducting\ud heterostructures, based on Ba0.9Nd0.1CuO2+x and CaCuO2 individual\ud blocks, using undulator radiation from a third-generation synchrotron.\ud We investigated films with different thicknesses of the intermediate\ud CaCuO2 block, grown on (001)SrTiO3 substrates by the pulsed-laser\ud deposition technique with no in situ diagnostic. In this communication\ud we demonstrate that the thickness of such heterostructures can be\ud controlled at the single unit cell level. This analysis shows that the\ud interfaces between the different constituent blocks are very sharp with\ud roughness less than one unit cell. (C) 2003 American Institute of\ud Physics

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Structural characterization of ultrathin cuprate artificial superconducting structures by x-ray synchrotron radiation

Aruta

Angeloni²,

Balestrino³

et al. 2003

Journal of Applied Physics

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“…Two sintered powder targets, with a nominal composition of Ba 0:9 Nd 0:1 CuO 2 and CaCuO 2 , mounted on a multitarget system, were used. The substitution of 10% of the Ba atoms with trivalent Nd cations, even if not strictly necessary for superconductivity [11,12], helped us to find the right growth conditions by slightly decreasing the uncompensation of the electrical charge in the CR block. The growth temperature was about 640 C and the molecular oxygen pressure was 1 mbar.…”

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Magnetic Imaging of Pearl Vortices in Artificially Layered(Ba0.9Nd0.1CuO2+x)

et al. 2004

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We have used scanning SQUID magnetometry to image vortices in ultrathin Ba 0:9 Nd 0:1 CuO 2x m = CaCuO 2 n high temperature superconductor samples, with as few as three superconducting CuO 2 planes. The Pearl lengths ( 2 2 L =d, L the London penetration depth, d the superconducting film thickness) in these samples, as determined by fits to the vortex images, agree with those by local susceptibility measurements, and can be as long as 1 mm. The in-plane penetration depths ab inferred from the Pearl lengths are longer than many bulk cuprates with comparable critical temperatures. We speculate on the causes of the long penetration depths, and on the possibility of exploiting the unique properties of these superconductors for basic experiments. DOI: 10.1103/PhysRevLett.92.157006 PACS numbers: 74.72.-h, 73.40.Gk, 73.40.Rw, 74.50.+r Vortices play a central role in many aspects of superconductivity. Not only do the dynamics of vortices determine many of the transport properties of type II superconductors, especially the high critical temperature cuprates [1], but vortices are also of more general interest, since as topological defects they are of great relevance, for instance, to phase transitions [2,3]. The formation of topological defects in phase transitions has even stimulated some analogies between cosmology, gauge theories, and condensed matter physics [4,5]. Vortices in bulk type II superconductors were first predicted by Abrikosov in 1957 [6], and have since been imaged by many different experimental techniques [7]. Vortices in thin superconductors (d L , where d is the superconducting film thicknes and L the London penetration depth, respectively) were first described by Pearl [8] (hence ''Pearl'' vortices). Pearl vortices have several interesting attributes. The field strengths h z perpendicular to the films diverge as 1=r at distances r in Pearl vortices, whereas in Abrikosov vortices the fields diverge as lnr= L [9]. Since in the Pearl vortex much of the vortex energy is associated with the fields outside of the superconductor, the interaction potential V int r between Pearl vortices has a long range component V int =r for r[8], unlike Abrikosov vortices, which have only short range interactions. The interaction between Pearl vortices V int ln=r for r leads to a BerezinskiiKosterlitz-Thouless (BKT) transition which is cut off due to screening on a scale [1]. The logarithmic interaction makes this system very similar to a Coulomb gas and ideal to study screening effects and renormalization in BKT transitions [10]. While superconducting vortices in films with thickness d comparable to the London penetration depth L have been imaged using many techniques, to our knowledge the present work is the first to directly demonstrate experimentally the existence of Pearl vortices for d , and is also the first to use scanning susceptibility measurements to determine penetration depths in superconductors.In the present work, two different types of Ba 0:9 Nd 0:1 CuO 2x m =CaCuO 2 n (CBCO) structures were grown: (a) t...

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“…They consist of one superconducting infinite layer block (two CaCuO 2 unit cells), sandwiched between two charge reservoirs (5 Ba-based unit cells). The structure was grown on (001) SrTiO 3 substrates, with nominally zero miscut angle, by using a focussed KrF excimer pulsed laser source [4,5]. The films were photolithographically patterned into bridges.…”

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Dissipation in ultra-thin current-carrying superconducting bridges; evidence for quantum tunneling of Pearl vortices

Tafuri¹,

Kirtley

Born³

et al. 2006

Europhys. Lett.

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We have made current-voltage (IV) measurements of artificially layered high-Tc thin-film bridges. Scanning SQUID microscopy of these films provides values for the Pearl lengths Λ that exceed the bridge width, and shows that the current distributions are uniform across the bridges. At high temperatures and high currents the voltages follow the power law V ∝ I n , with n = Φ 2 0 /8π 2 ΛkBT +1, and at high temperatures and low-currents the resistance is exponential in temperature, in good agreement with the predictions for thermally activated vortex motion. At low temperatures, the IV's are better fit by ln V linear in I −2 . This is expected if the low temperature dissipation is dominated by quantum tunneling of Pearl vortices.

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Superconductivity in ultrathin artificial cuprate structures

Cited by 22 publications

References 21 publications

Structural characterization of ultrathin cuprate artificial superconducting structures by x-ray synchrotron radiation

Structural characterization of ultrathin cuprate artificial superconducting structures by x-ray synchrotron radiation

Magnetic Imaging of Pearl Vortices in Artificially Layered(Ba0.9Nd0.1CuO2+x)

Dissipation in ultra-thin current-carrying superconducting bridges; evidence for quantum tunneling of Pearl vortices

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