Resistive superconducting transition of single unit-cell YBa2Cu3O7−δ layers

Repaci, J. M.; Kwon, C.; Li, Qi; Jiang, Xiuguang; Venkatessan, T.; Glover, R. E.; Lobb, C. J.

doi:10.1007/bf02562968

Cited by 4 publications

(6 citation statements)

References 3 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] For example, a few unit-cell (UC) -thick YBa 2 Cu 3 O 7−x (YBCO) films sandwiched between semiconducting or insulating layers have broader resistive transitions than thicker ones, which has been attributed to the BKT physics. [4][5][6] The same explanation was proposed for the observation of nonlinear current-versusvoltage (I -V ) characteristics in YBCO, BiSrCaCuO, and TlBaCaCuO single crystals and thin films (see Ref.…”

Section: Introductionmentioning

confidence: 99%

“…This has been a matter of substantial debate, however. For example, Repaci et al 8 found the I -V characteristics to be Ohmic even in 1-UC-thick YBCO films at temperatures below the critical temperature (T c ), indicating the absence of the BKT transition. Subsequently, however, it was shown that at low currents, the addition of current noise can turn nonlinear I -V curves into Ohmic behavior.…”

Section: Introductionmentioning

confidence: 99%

“…It was recently shown that the size effects may radically alter the I -V curves of superconducting films 10 so that they mimic the BKT behavior. Further, it was noted that a precondition 8 for the BKT transition to occur in a superconductor, i.e., that the sample size L s < λ eff , where λ eff = 2λ 2 /d is the effective (Pearl) penetration depth and d is the film thickness, is not satisfied even in 1-UC-thick YBCO films. 11 Next, Davis et al 13 made a detailed comparison of the experimental data taken from YBCO films 12 with the BKT theory and found disagreement, which was attributed to inhomogeneity and vortex pinning.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic field and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4<

Gasparov

Božović

2012

Phys. Rev. B

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We used atomic-layer molecular beam epitaxy to synthesize bilayers of a cuprate metal (La 1.55 Sr 0.45 CuO 4 ) and a cuprate insulator (La 2 CuO 4 ) film, in which each layer is just one unit cell thick. We have studied the magnetic field and temperature dependences of the complex sheet conductance, σ (ω), of these films. Experiments have been carried out at frequencies between 2 and 20 MHz using the single-spiral coil technique. We found that (i) the inductive response, L −1 k (T ), starts at 1.7 K lower temperatures than Reσ (T ), which in turn is characterized by a peak close to the transition, (ii) this shift is almost constant with magnetic field up to 8 T; (iii) the vortex diffusion constant D(T ) is not linear with T at low temperature, as in the case of free vortices, but rather is exponential due to pinning of vortex cores, and (iv) the Berezinski-Kosterlitz-Thouless (BKT) transition temperature occurs at the point where Y = (l ω /ξ + ) 2 = 1. Our experimental results can be described well by the extended dynamic theory of the BKT transition and the dynamics of bound vortex-antivortex pairs with short separation lengths.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic field and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4<

Gasparov

Božović

2012

Phys. Rev. B

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“…3,[5][6][7][8] Even if earlier works 6,8,10 showed conclusively that ultrathin YBCO and BSCCO layers containing two CuO 2 planes were superconducting, nevertheless, the role played by the interlayer coupling, namely the coupling existing between two successive conducting blocks, relative to superconducting properties, remains debated. In the case of BSCCO 2212, though its superconductivity is found to be truly twodimensional in many reports, 9 transport measurements show a decrease of the critical temperature in the case of ultrathin films.…”

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confidence: 99%

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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“…The low-current ohmic V(I) signal in ultrathin YBaCuO films was attributed to the vanishing of the logarithmic interaction between vortices and antivortices at large separations, 24 which can lead to the existence of free vortices at all temperatures, in the absence of relevant pinning. Such free vortices should generate Arrhenius behavior in the (T) plot, but, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 1998
Phys. Rev. B
13
0
6
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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Resistive superconducting transition of single unit-cell YBa2Cu3O7−δ layers

Cited by 4 publications

References 3 publications

Magnetic field and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4<

Magnetic field and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4<

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
13
0
6
0
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Resistive superconducting transition of single unit-cell YBa2Cu3O7−δ layers

Cited by 4 publications

References 3 publications

Magnetic field and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4<

Magnetic field and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4<

Interlayer coupling in ultrathin high-Tcartificial structures

Length-scale-dependent vortex-antivortex unbinding in epitaxialBi2Sr2CaCuMiu1, Jakob2, Haibach3 et al. 1998Phys. Rev. B13060View full textAdd to dashboardCite

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

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