Superconducting glassy state in high-Tc oxides

Müller, K. A.; Blazey, K. W.; Bednorz, J. G.; Takashige, Masaaki

doi:10.1016/0378-4363(87)90180-x

Cited by 42 publications

(33 citation statements)

References 23 publications

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“…The phase factors A;~=X,&II introduce randomness for H&0 because K;J is a random geometric factor. A review of the superconducting glass rate has recently appeared (Miiller, Blazey, Bednorz, and Takashige, 1987). The first experimental evidence indicating the presence of superconducting glassy behavior was deduced from field-cooled and zero-field-cooled magnetization data (Muller, Takashige, and Bednorz, 1987;Razavi et al , 1987) in La2 Ba CuO"ceramics.…”

Section: Figurementioning

confidence: 99%

Perovskite-type oxides—The new approach to high-Tcsuperconductivity

1988

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In our Lecture we take the opportunity to describe the guiding ideas and our effort in the search for high-T, superconductivity. They directed the way from the cubic niobium-containing alloys to layered copper-containing oxides of perovskite-type structure. We shall also throw some light onto the circumstances and the environment which made this breakthrough possible. In the second part, properties of the new superconductors are described. THE BACKGROUND At IBM's Zurich Research Laboratory, there had been a tradition of more than two decades of research efforts in insulating oxides. The key materials under investigation were perovskites like SrTi03 and LaA103, used as model crystals to study structural and ferroelectric phase transitions. The pioneering ESR experiments by Alex Miiller (KAM; see Miiller, 1971) and W. Berlinger on transition-metal impurities in the perovskite host lattice brought substantial insight into the local symmetry of these crystals, i,e. , the rotations of the TiO6 octahedra, the characteristic building units of the lattice. One of us (KAM) first became aware of the possibility of high-temperature superconductivity in the 100-K range by the calculations of T. Schneider and E. Stoll on metallic hydrogen (Schneider and Stoll, 1971). Such a hydrogen state was estimated to be in the 2-3 Mbar range.. Subsequent discussions with T. Schneider on the possibility of incorporating sufFicient hydrogen into a high-dielectric-constant material like SrTiO3 to induce a metallic state led, however, to the conclusion that the density required could not be reached. While working on my Ph. D. thesis at the Solid State Physics Laboratory of the ETH Zurich, I (JGB) gained my first experience in low-temperature experiments by studying the structural and ferroelectric properties of perovskite solid-solution crystals. It was fascinating to learn about the large variety of properties of these materials and how one could change them by varying their compositions. The key material, pure SrTi03, could even be turned into a superconductor if it were reduced, i.e. , if oxygen were partially removed from its lattice (Schooley et al. , 1967). The transition temperature of 0.3 K, how-*This lecture was delivered 8 December 1987, on the occasion of the presentation of the 1987 Nobel Prize in Physics. ever, was too low to create large excitement in the world of superconductivity research. Nevertheless, it was interesting that superconductivity occurred at all, because the carrier densities were so low compared to superconducting NbO, which has carrier densities like a normal metal. My personal interest in the fascinating phenomenon of superconductivity was triggered in 1,978 by a telephone call from Heinrich Rohrer, the manager of a new hire at IBM Riischlikon, Gerd Binnig. With his background in superconductivity and tunneling, Gerd was. interested in studying the superconductive properties of SrTiO3, especially in the case when the carrier density in the system was increased. For me this was the start of a short but stimul...

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Section: Figurementioning

confidence: 99%

Perovskite-type oxides—The new approach to high-Tcsuperconductivity

1988

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“…In particular, the effects of self-organization in network glasses have been successfully simulated numerically 10 . The experimental effects described above (the EMA single continuous transition splits into two transitions; with increasing doping 4 or connectivity, the first transition is continuous and the second is first order) are actually obtained in these simulations, which are illustrated for the reader's convenience in Figs. 1 and 2.…”

Section: Introductionmentioning

confidence: 99%

Zigzag filamentary theory of broken symmetry of neutron and infrared vibronic spectra of YBa₂Cu₃O_6+x

Phillips

Jung

2002

Philosophical Magazine B

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Filamentary high-temperature superconductor (HTSC) theory differs fundamentally from continuous HTSC theories because it emphasizes self-organized, discrete dopant networks and does not make the effective medium approximation (EMA). Analysis of neutron and infrared (especially with c-axis polarization) vibrational spectra, primarily for YBa 2 Cu 3 O 6+x , within the filamentary framework, shows that the observed vibronic anomalies near 400 cm -1 (50 meV) are associated with curvilinear filamentary paths.These paths pass through the cuprate chains and planes, as well as resonant tunneling centers in the BaO layers. The analysis and the data confirm earlier filamentary structural models containing ferroelastic domains of diameter 3-4 nm in the CuO 2 planes; it is these nanodomains that are responsible for the discrete glassy nature of both electronic and vibrational properties. Chemical trends in vibronic energies and oscillator strengths, both for neutron and photon scattering, that were anomalous in continuum models, are readily explained by the filamentary model.

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“…How can we characterize these filaments topologically? Because of their multinary chemistry and perovskite structures, HTSC and CMR compounds contain a high density, and wide variety, of spatial inhomogeneities (Mueller et al, 1987). One might picture the self-organized filaments as avoiding randomly distributed phase-separated obstacles, but this picture is incomplete because the results could depend on the sizes and densities of the obstacles.…”

Section: Fractal Description Of Non-drude Conductivitymentioning

confidence: 99%

Fractal nature and scaling exponents of non-Drude currents in non-Fermi liquids

Phillips¹

2001

Philosophical Magazine B

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In many oxides of the perovskite and pseudoperovskite families there are phase transitions between insulating and normal metallic (Fermi-liquid) phases that are separated by an intermediate phase that is often called a non-Fermi liquid. The dc resistivity of the intermediate or non-Fermi-liquid phase often exhibits a T temperature dependence, in contrast with the T 2 dependence expected from a bad normal metal. The same alloys exhibit a non-Drude ! 2¬ frequency dependence, with ¬ º 0:5, in contrast with the Drude dependence ! 2 characteristic of samples with the T 2 behaviour. Various attempts have been made to modify the algebra of continuum Fermi-liquid theory to derive the non-Drude exponent ¬, but these have been based on arti®ces designed to explain only this one parameter. The discrete ®lamentary model has been used to calculate many properties of high-temperature superconductors, and to explain the asymmetric nature of the intermediate phase.Here it is used to derive ¬ by the same rules previously used for several other discrete relaxation calculations that are in excellent agreement with other quite diOE erent experiments. The results are, for (cubic) perovskites, ¬ˆ0:45 and, for planar conductivity of bilayered pseudoperovskites, ¬ˆ0:70. The corresponding experimental values are (0.4, 0.5) and 0.7. } 1. Introduction The discovery of high-temperatur e superconductivity (Bednorz and Mueller 1986) has led further to the discovery of many allied normal-state transport anomalies, which are characteristically found in oxides with the (nearly) cubic perovskite or related (nearly) tetragonal layered pseudoperovskit e structures. Some attempts to understand the origin of high-temperatur e superconductivity and the closely related phenomenon of colossal magnetoresistanc e (CMR) have therefore focused on these latter normal-state transport anomalies. However, so far many theoretical models stress the importance of electron±electron interactions, as summarized by Metzer et al. (1998), Disertori andRivasseau (2000) and Farid (2000). These theories have been formulated only in the context of continuum models in momentum space that idealize the materials as black boxes (the eOE ective-medium approximation) , with results that closely resemble Fermi-liquid theory (FLT), which itself gives a good account of normal metallic transport without anomalies. Continuum attempts to discuss the anomalies are thus forced to introduce various arti®ces, especially with regard to relaxation time anisotropies in momentum space (IoOE e and Millis 1998), that have no general signi®cance and amount to contriving as many constructs as there are observables.The distinction between continuous and discrete structures is fundamental in all theories of transport in solids. In simple metals transport theory is always based on continuum models in momentum space, with the interaction between current carriers and impurities being treated by perturbation theory. However, in the limit T ! 0 near the metal±insulator transition in semiconductor impuri...

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Superconducting glassy state in high-Tc oxides

Cited by 42 publications

References 23 publications

Perovskite-type oxides—The new approach to high-Tcsuperconductivity

Perovskite-type oxides—The new approach to high-Tcsuperconductivity

Zigzag filamentary theory of broken symmetry of neutron and infrared vibronic spectra of YBa₂Cu₃O_6+x

Fractal nature and scaling exponents of non-Drude currents in non-Fermi liquids

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Superconducting glassy state in high-Tc oxides

Cited by 42 publications

References 23 publications

Perovskite-type oxides—The new approach to high-Tcsuperconductivity

Perovskite-type oxides—The new approach to high-Tcsuperconductivity

Zigzag filamentary theory of broken symmetry of neutron and infrared vibronic spectra of YBa2Cu3O6+x

Fractal nature and scaling exponents of non-Drude currents in non-Fermi liquids

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Zigzag filamentary theory of broken symmetry of neutron and infrared vibronic spectra of YBa₂Cu₃O_6+x