An enhancement of Tc, from 45 K to 70 K, via Cd substitution in (Pb, Cu)Sr2(Ca, Y)Cu2O7−δ

Liu, R. S.; Groult, D.; Maignan, A.; Hu, Shu‐Fen; Jefferson, D. A.; Raveau, B.; Michel, C.; Hervieu, M.; Edwards, Peter P.

doi:10.1016/0921-4534(92)90070-s

Cited by 51 publications

(16 citation statements)

References 26 publications

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“…Hanamura [10] investigated theoretically the radiative decay rate of quantum dot and quantum well. The obtained results are in agreement with that of Lee and Liu's [7] prediction for thin films. Knoester [11] studied the radiative dynamics crossover from the small thickness, superradiant exciton regime to bulk crystal, polariton regime.…”

supporting

confidence: 91%

“…What makes the excitons trapped in the bulk crystal is the conservation of crystal momentum. If one considers a thin film [7], the excitons can undergo radiative decay as a result of the broken crystal symmetry along the normal direction of the film plane. The decay rate of excitons in a thin film is enhanced by a factor of (λ/d) 2 compared to a lone exciton in an empty lattice, where λ is the wave length of emitted photon and d is the lattice constant of the film.…”

mentioning

confidence: 99%

“…Therefore, one can first consider the exciton as a particle with angular momentum ν and longitudinal momentum k z . After figuring out the decay rate and frequency shift of a Frenkel exciton, the corresponding ones of a Wannier Exciton can be obtained by replacing the single-atom dipole matrix element χ with the effective dipole matrix element [7]. Thus, the Hamiltonian for the exciton is…”

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confidence: 99%

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Decay rate and renormalized frequency shift of superradiant exciton in a cylindrical quantum wire

Chen¹,

Chuu²

2003

Physica B: Condensed Matter

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The decay rate and renormalized frequency shift of superradiant exciton in a cylindrical quantum wire are studied. The transition behavior from 1D wire to 2D film is examined through the property of the radiative decay. Similar to the case in a quantum well, the decay rate of the higher mode exciton is larger than that of the lower mode one. Moreover, it is also found the decay rate and frequency shift do not show oscillatory dependence on wire radius because of the conservation of angular momentum.

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confidence: 91%

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Decay rate and renormalized frequency shift of superradiant exciton in a cylindrical quantum wire

Chen¹,

Chuu²

2003

Physica B: Condensed Matter

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“…The bidimensional character of the structure and the mixed valence of copper are two essential parameters for superconductivity. Therefore [2][3][4][5][6][7] and for x = 0.3, M = Sc and Fe [8]. These cuprates exhibit a rock salt-type slice built from one mixed [Pbl_xMxO] layer surrounded by two [SrO] layers.…”

Section: Introductionmentioning

confidence: 99%

Mixed Layers in Copper Based Superconducting Materials

Hervieu

Tendeloo

Michel

et al. 1996

Microsc. Microanal. Microstruct.

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Abstract. 2014 Recently discovered series of high Tc superconductors, characterized by the existence of two types of cations within the same layer, are presented. The first family concerns the mercury based cuprates, Hg1-xMxA2Cam-1CumO2m+2+03B4, with A = Ba and/or Sr, which exhibit structures closely related to that of the thallium cuprates TlBa2Cam-1CumO2m+3. They differ from the thallium cuprates by a high oxygen deficiency at the level of the mercury layer. It is shown that cations such as M = Cu, Pb, Tl, Bi, Ce, Pr, Cr, V, Mo, W, Ti, Sr, Ca,... can partially substitute for mercury ions, stabilizing the structures. The cationic composition of the layer depends indeed on the nature of the M cation but also on that of the alkaline earth A. For given A and M cations, the x value remains unchanged even when the number of copper layers varies. M and Hg cations are either statistically distributed over the same site or ordered. Different types of ordering have been detected. Another way of generating mixed layers is to shear periodically the structure, leading to the formation of the so called "collapsed phase". In the collapsed bismuth cuprates, bismuth and copper segments, a few octahedra long, alternate in strongly waving layers. In the collapsed oxycarbonates, carbonate groups and M cations are ordered within the intermediate layer so that they can be simply described from a partial and ordered substitution of carbon for Hg,Tl, Bi and other M cations building the intermediate layer. The oxycarbonitrates (Y1-xCax)nBa2nCu3n-1(C,N)O3O7n-3 can also be described as an ordered substitution of carbon for copper in the 123 matrix. The different families of superconducting materials which are generated by such mechanisms are described as well as the way the different species are distributed within the mixed layers. Their influence on the physical properties are discussed.

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“…Motivated by these experimental results, we have explored new substitution elements for Nb sites to induce superconductivity in the Nb-1212 system. Considering a similar role between Cd and Cu substitutions in charge reservoir layers in superconducting cuprates [9,10], we attempted at first to induce superconductivity in the (Nb 1-x Cu x ) Sr 2 EuCu 2 O z (x 0.5) system by Cu substitution instead of Cd for Nb, but this was unsuccessful. However, we have newly discovered that superconductivity can be induced in the Ti and Cu co-doped NbSr 2 EuCu 2 O z samples.…”

Section: Introductionmentioning

confidence: 99%