Local lattice instability and superconductivity in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>La</mml:mtext></mml:mrow><mml:mrow><mml:mn>1.85</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Sr</mml:mtext></mml:mrow><mml:mrow><mml:mn>0.15</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Cu</mml:mtext></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi

Zhang, C. J.; Ōyanagi, H.

doi:10.1103/physrevb.79.064521

Cited by 73 publications

(102 citation statements)

References 32 publications

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“…When the CuO 2 layers were under compressive strain (so that the critical axial zag paths were under tensile strain, and thus more flexible), this is what was observed as T decreased well below T c , where the superconductive energy is largest. Very similar effects appear in the FeAs family as well [59]; a more extensive percolative discussion will be given elsewhere.…”

Section: Single-layer Cuprates: Mechanically Marginally Unstable (Mmu)mentioning

confidence: 68%

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Hard-Wired Dopant Networks and the Prediction of High Transition Temperatures in Ceramic Superconductors

Phillips

2010

J Supercond Nov Magn

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I review the multiple successes of the discrete hard-wired dopant network model ZZIP, and comment on the equally numerous failures of continuum models, in describing and predicting the properties of ceramic superconductors. The prediction of transition temperatures can be regarded in several ways, either as an exacting test of theory, or as a tool for identifying theoretical rules for defining new homology models. Popular "first principle" methods for predicting transition temperatures in conventional crystalline superconductors have failed for cuprate HTSC, as have parameterized models based on CuO 2 planes (with or without apical oxygen). Following a path suggested by Bayesian probability, it was found that the glassy, self-organized dopant network percolative model is so successful that it defines a new homology class appropriate to ceramic superconductors. The reasons for this success in an exponentially complex (non-polynomial complete, NPC) problem are discussed, and a critical comparison is made with previous polynomial (PC) theories. The predictions are successful for the superfamily of all ceramics, including new non-cuprates based on FeAs in place of CuO 2 .

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Section: Single-layer Cuprates: Mechanically Marginally Unstable (Mmu)mentioning

confidence: 68%

“…The coupling of HTSC to lattice disorder (not order!) is directly and elegantly shown in [59]. Superconductive formation and overlap of zigzag percolative filamentary arrays can increase lattice disorder.…”

Section: Single-layer Cuprates: Mechanically Marginally Unstable (Mmu)mentioning

confidence: 90%

Hard-Wired Dopant Networks and the Prediction of High Transition Temperatures in Ceramic Superconductors

Phillips

2010

J Supercond Nov Magn

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“…Although SrTiO 3 (STO) is not a high temperature superconductor, it is a ceramic that exhibits superconductivity with T max c ∼ 0.5 K at very low carrier densities n 3D ∼ ð10 18 -10 20 Þ∕cm 3 , in both chemically doped bulk and electric-field induced surface accumulation layers (31). The coincidence of the chemically doped and electric-field induced surface T max c values could be accidental, but there is a natural percolative explanation for this coincidence: T max c is reached when the percolative filaments begin to merge, just as in the EXAFS data for HTSC (26,27).…”

Section: Discussionmentioning

confidence: 87%

Percolative theories of strongly disordered ceramic high-temperature superconductors

Phillips

2010

Proc. Natl. Acad. Sci. U.S.A.

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Optimally doped ceramic superconductors (cuprates, pnictides, etc.) exhibit transition temperatures T c much larger than strongly coupled metallic superconductors like Pb (T c ¼ 7.2 K, E g ∕kT c ¼ 4.5) and exhibit many universal features that appear to contradict the Bardeen, Cooper, and Schrieffer theory of superconductivity based on attractive electron-phonon pairing interactions. These complex materials are strongly disordered and contain several competing nanophases that cannot be described effectively by parameterized Hamiltonian models, yet their phase diagrams also exhibit many universal features in both the normal and superconductive states. Here we review the rapidly growing body of experimental results that suggest that these anomalously universal features are the result of marginal stabilities of the ceramic electronic and lattice structures. These dual marginal stabilities favor both electronic percolation of a dopant network and rigidity percolation of the deformed lattice network. This "double percolation" model has previously explained many features of the normal-state transport properties of these materials and is the only theory that has successfully predicted strict lowest upper bounds for T c in the cuprate and pnictide families. Here it is extended to include Coulomb correlations and percolative band narrowing, as well as an angular energy gap equation, which rationalizes angularly averaged gap∕T c ratios, and shows that these are similar to those of conventional strongly coupled superconductors. percolation | theoryA ll known microscopic theories of metallic superconductors are based on the isotropic Bardeen, Cooper, and Schrieffer (BCS) model of Cooper pairs formed by attractive electronphonon interactions that overwhelm repulsive Coulomb interactions, yet many features of electron-phonon interactions in the BCS theory that are confirmed in metals appear to be weak or absent in the infrared spectra of ceramic layered high temperature superconductors (HTSC) (1). The ceramics often exhibit multiple phases and must be doped to be not only superconductive but even metallic. By contrast layered undoped MgB 2 with T c ∼ 40 K is an "ideal" example of a metallic BCS crystalline superconductor where T c can be calculated quite accurately (2). When MgB 2 is substitutionally doped with ∼10% Al (on the Mg sites) or C (on the B sites), T c decreases drastically to ∼10 K (3). Many authors have invoked residual spin interactions in the doped state, left over from the magnetic undoped states, as a source of this difference (1). However, it has been known for a long time that electron-spin interactions (for instance, with magnetic impurities) drastically suppress T c by breaking S ¼ 0 Cooper pairs (4), and more generally that the insulating antiferromagnetic (AF) and metallic Cooper pair four-particle plaquette channels are completely independent (5). While ceramics often exhibit multiple phases, recently the data have shifted overwhelmingly in favor of phonon exchange as the only attractive interaction cor...

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“…The in-plane Cu--O bonds show unconventional broadening at low temperature, which is connected with dynamic lattice instability related to superconductivity [11,12]. Moreover this instability was interpreted as anharmonicity-induced multiphonon processes [13] and as oxygen ion vibration in a double-well potential in some investigations [7][8][9][10].…”

Section: Introductionmentioning

confidence: 98%

“…Considerable quantity of the EXAFS evidences for the existence of low-temperature local structure anomalies of CuO 2 plane in hole-doped HTSC-cuprates was reported up to date [6][7][8][9][10][11][12]. The in-plane Cu--O bonds show unconventional broadening at low temperature, which is connected with dynamic lattice instability related to superconductivity [11,12].…”

Section: Introductionmentioning

confidence: 99%

Correlation of the local and the macroscopic properties of high-temperature superconductors

Менушенков¹,

Kuznetsov

Chernikov

et al. 2010

Zeitschrift Für Kristallographie

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Abstract. Temperature dependent comparative EXAFS studies of Ba 1Àx K x BiO 3 superconducting oxides and copper based superconductors with hole (La 2Àx Sr x CuO 4 ) and electron (Nd 2Àx Ce x CuO 4Àd ) doping showed the common dynamical local structure nonuniformity observed as the double-well potential of oxygen ion oscillations. Obtained data evidence that these local structure nonuniformity arises from the local dynamic charge ordering due to different electronic structure of the neighbouring BiO 6 or CuO n (n ¼ 4; 6) complexes in perovskite-like lattice. Based on the experimental results, the phenomenological description was proposed which allowed us to establish the correlations between the local and the macroscopic properties and to explain the insulator-metal phase transition and the appearance of the superconductive state with both hole and electron doping of parent BaBiO 3 , La 2 CuO 4 and Nd 2 CuO 4 insulators. The presented results makes clear the role of electron-phonon coupling in the mechanism of high temperature superconductivity.

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Local lattice instability and superconductivity inLa1.85Sr0.15Cu1−x

Cited by 73 publications

References 32 publications

Hard-Wired Dopant Networks and the Prediction of High Transition Temperatures in Ceramic Superconductors

Hard-Wired Dopant Networks and the Prediction of High Transition Temperatures in Ceramic Superconductors

Percolative theories of strongly disordered ceramic high-temperature superconductors

Correlation of the local and the macroscopic properties of high-temperature superconductors

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