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Balestrino, G.; Martellucci, S.; Medaglia, P. G.; Paoletti, A.; Petrocelli, G.; Varlamov, A. A.

doi:10.1103/physrevb.58.r8925

Cited by 43 publications

(31 citation statements)

References 14 publications

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“…It was found that, the maximum value of T c is obtained for Nϭ3 and that, increasing N, the IL superconducting block becomes more and more underdoped, finally giving rise to an insulating behavior for NϾ12. 14,15 For the present study ͓͑Ba 0.9 , Nd 0.1 ͒CuO 2ϩx ͔ m /͓CaCuO 2 ͔ 2 (mϫ2) superlattices were deposited varying m in order to investigate the role of the coupling between successive (CaCuO 2 ) 2 conducting blocks. Thus the distance between successive IL blocks ranges from 8.5 Å ͑2ϫ2 superlattices͒ to 21 Å ͑5ϫ2 superlattices͒.…”

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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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confidence: 99%

Interlayer coupling in ultrathin high-Tcartificial structures

Balestrino¹,

Lavanga²,

Medaglia³

et al. 2001

Phys. Rev. B

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“…The overall experimental studies have suggested that the superconductivity is mainly confined at the interface between CCO and STO [6,[10][11][12]. Differently from previous cuprate/cuprate heterostructures [5,13,14], now the spacer between the superconducting blocks is not a cuprate, but it is STO. The CCO/STO interfaces are thus very similar to the IL/CR native interface of HTS.…”

mentioning

confidence: 99%

High-TcSuperconductivity at the Interface between theCaCuO2and
Castro
¹
,
Cantoni
²
,
Ridolfi
³

et al. 2015
Phys. Rev. Lett.
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At interfaces between complex oxides it is possible to generate electronic systems with unusual electronic properties, which are not present in the isolated oxides. One important example is the appearance of superconductivity at the interface between insulating oxides, although, until now, with very low T c . We report the occurrence of high T c superconductivity in the bilayer CaCuO 2 /SrTiO 3 , where both the constituent oxides are insulating. In order to obtain a superconducting state, the CaCuO 2 /SrTiO 3 interface must be realized between the Ca plane of CaCuO 2 and the TiO 2 plane of SrTiO 3 . Only in this case extra oxygen ions can be incorporated in the interface Ca plane, acting as apical oxygen for Cu and providing holes to the CuO 2 planes. A detailed hole doping spatial profile has been obtained by STEM/EELS at the O K-edge, clearly showing that the (super)conductivity is confined to about 1-2 CaCuO 2 unit cells close to the interface with SrTiO 3 . The results obtained for the CaCuO 2 /SrTiO 3 interface can be extended to multilayered high T c cuprates, contributing to explain the dependence of T c on the number of CuO 2 planes in these systems. 2The interface between complex transition metal oxides is recently emerging as one of the most interesting systems in condensed matter physics [1]. Indeed, a range of fascinating interface electronic phenomena, as high mobility two-dimensional electron gas, quantum Hall effect, and superconductivity, have all been discovered in oxide hererostructures [2][3][4][5][6][7][8], but are absent in either of their constituents. One interesting example is the formation of a conducting quasi-two-dimensional electron gas at the interface between the insulating perovskites LaAlO 3 and SrTiO 3 [2]. Strikingly, this interface is also superconducting with transition temperature (T c ) about 10 -1 K [4,9].On the other hand, the layered structure of cuprate high T c superconductors (HTS) can be schematized as a sequence of natural interfaces between two blocks with different structure and functionality: an insulating block with "infinite layers" (IL) structure, i.e., containing a sequence of In this work, by using state-of-the-art aberration-corrected scanning transmission electron microscopy (STEM) coupled to electron energy loss spectroscopy (EELS), we investigate the CCO/STO interface present in the bilayer (CCO) n /(STO) m , with unprecedent spatial resolution [16].We find that this interface shows high T c superconductivity, with optimal T c about 40 K, a value smaller, but still comparable with those found in the [(CaCuO 2 ) n /(SrTiO 3 ) m ] N superlattices [6,10]. Wegive direct evidence that charge doping, and therefore superconductivity, are realized through the introduction of extra oxygen ions at the CCO/STO interface, giving rise to a CaO x atomic plane

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“…For larger n values, T c (n) shows a smooth decrease, which is well explained taking into account the decrease of the effective hole concentration per single CuO 2 plane due to the increase of the total number of CuO 2 planes in the IL block. 17 For nϽ2, T c shows a sharp drop. A striking result of this investigation was that the occurrence of a non integer number n of CaCuO 2 unit cells in the IL block does not affect the T c of these artificial structures.…”

Section: Introductionmentioning

confidence: 94%

Structural features of(Ba2Cu2O4
Balestrino¹,
Pasquini²,
Tebano³
2000
Phys. Rev. B
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The structural disorder in (Ba 2 Cu 2 O 4ϩx )/(CaCuO 2 ) n superlattices with ultrathin individual layers consisting of a noninteger number of unit cells is investigated. X-ray diffration and reflection high energy electron diffraction show that a two-dimensional layer by layer growth occurs and that layers of mixed composition are corrugated to adjust the internal stresses. On the basis of these conclusions we can outline an explanation for the behavior of T c vs n in (Ba 2 Cu 2 O 4ϩx )/(CaCuO 2 ) n superlattices.

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Dependence of the critical temperature onnin(BaCuO2

Cited by 43 publications

References 14 publications

Interlayer coupling in ultrathin high-Tcartificial structures

Interlayer coupling in ultrathin high-Tcartificial structures

High-TcSuperconductivity at the Interface between theCaCuO2and
Castro
¹
,
Cantoni
²
,
Ridolfi
³

et al. 2015
Phys. Rev. Lett.
Self Cite

Structural features of(Ba2Cu2O4
Balestrino¹,
Pasquini²,
Tebano³
2000
Phys. Rev. B
Self Cite
17
0
8
0
View full text Add to dashboard Cite

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Dependence of the critical temperature onnin(BaCuO2

Cited by 43 publications

References 14 publications

Interlayer coupling in ultrathin high-Tcartificial structures

Interlayer coupling in ultrathin high-Tcartificial structures

High-TcSuperconductivity at the Interface between theCaCuO2andCastro1, Cantoni2, Ridolfi3 et al. 2015Phys. Rev. Lett.Self Cite

Structural features of(Ba2Cu2O4Balestrino1, Pasquini2, Tebano3 2000Phys. Rev. BSelf Cite17080View full textAdd to dashboardCite

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About

High-TcSuperconductivity at the Interface between theCaCuO2and
Castro
¹
,
Cantoni
²
,
Ridolfi
³

et al. 2015
Phys. Rev. Lett.
Self Cite

Structural features of(Ba2Cu2O4
Balestrino¹,
Pasquini²,
Tebano³
2000
Phys. Rev. B
Self Cite
17
0
8
0
View full text Add to dashboard Cite