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Journal ArticleDOI

Superconductivity at 93 K in a new mixed-phase Y-Ba-Cu-O compound system at ambient pressure

02 Mar 1987-Physical Review Letters (American Physical Society)-Vol. 58, Iss: 9, pp 908-910
TL;DR: A stable and reproducible superconductivity transition between 80 and 93 K has been unambiguously observed both resistively and magnetically in a new Y-Ba-Cu-O compound system at ambient pressure.
Abstract: A stable and reproducible superconductivity transition between 80 and 93 K has been unambiguously observed both resistively and magnetically in a new Y-Ba-Cu-O compound system at ambient pressure. An estimated upper critical field H c2(0) between 80 and 180 T was obtained.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a review of the physics of high-temperature superconductors from the point of view of the doping of a Mott insulator is presented, with the goal of putting the resonating valence bond idea on a more formal footing.
Abstract: This article reviews the physics of high-temperature superconductors from the point of view of the doping of a Mott insulator. The basic electronic structure of cuprates is reviewed, emphasizing the physics of strong correlation and establishing the model of a doped Mott insulator as a starting point. A variety of experiments are discussed, focusing on the region of the phase diagram close to the Mott insulator (the underdoped region) where the behavior is most anomalous. The normal state in this region exhibits pseudogap phenomenon. In contrast, the quasiparticles in the superconducting state are well defined and behave according to theory. This review introduces Anderson's idea of the resonating valence bond and argues that it gives a qualitative account of the data. The importance of phase fluctuations is discussed, leading to a theory of the transition temperature, which is driven by phase fluctuations and the thermal excitation of quasiparticles. However, an argument is made that phase fluctuations can only explain pseudogap phenomenology over a limited temperature range, and some additional physics is needed to explain the onset of singlet formation at very high temperatures. A description of the numerical method of the projected wave function is presented, which turns out to be a very useful technique for implementing the strong correlation constraint and leads to a number of predictions which are in agreement with experiments. The remainder of the paper deals with an analytic treatment of the $t\text{\ensuremath{-}}J$ model, with the goal of putting the resonating valence bond idea on a more formal footing. The slave boson is introduced to enforce the constraint againt double occupation and it is shown that the implementation of this local constraint leads naturally to gauge theories. This review follows the historical order by first examining the U(1) formulation of the gauge theory. Some inadequacies of this formulation for underdoping are discussed, leading to the SU(2) formulation. Here follows a rather thorough discussion of the role of gauge theory in describing the spin-liquid phase of the undoped Mott insulator. The difference between the high-energy gauge group in the formulation of the problem versus the low-energy gauge group, which is an emergent phenomenon, is emphasized. Several possible routes to deconfinement based on different emergent gauge groups are discussed, which leads to the physics of fractionalization and spin-charge separation. Next the extension of the SU(2) formulation to nonzero doping is described with a focus on a part of the mean-field phase diagram called the staggered flux liquid phase. It will be shown that inclusion of the gauge fluctuation provides a reasonable description of the pseudogap phase. It is emphasized that $d$-wave superconductivity can be considered as evolving from a stable U(1) spin liquid. These ideas are applied to the high-${T}_{c}$ cuprates, and their implications for the vortex structure and the phase diagram are discussed. A possible test of the topological structure of the pseudogap phase is described.

3,246 citations


Cites background from "Superconductivity at 93 K in a new ..."

  • ...…discovery of high temperature superconductivity in cuprates (Bednorz and Mueller, 1986) and the rapid raising of the transition temperature to well above the melting point of nitrogen (Wu et al., 1987) ushered in an era of great excitement for the condensed matter physics community....

    [...]

Journal ArticleDOI
TL;DR: A review of the most recent ARPES results on the cuprate superconductors and their insulating parent and sister compounds is presented in this article, with the purpose of providing an updated summary of the extensive literature.
Abstract: The last decade witnessed significant progress in angle-resolved photoemission spectroscopy (ARPES) and its applications. Today, ARPES experiments with 2-meV energy resolution and $0.2\ifmmode^\circ\else\textdegree\fi{}$ angular resolution are a reality even for photoemission on solids. These technological advances and the improved sample quality have enabled ARPES to emerge as a leading tool in the investigation of the high-${T}_{c}$ superconductors. This paper reviews the most recent ARPES results on the cuprate superconductors and their insulating parent and sister compounds, with the purpose of providing an updated summary of the extensive literature. The low-energy excitations are discussed with emphasis on some of the most relevant issues, such as the Fermi surface and remnant Fermi surface, the superconducting gap, the pseudogap and $d$-wave-like dispersion, evidence of electronic inhomogeneity and nanoscale phase separation, the emergence of coherent quasiparticles through the superconducting transition, and many-body effects in the one-particle spectral function due to the interaction of the charge with magnetic and/or lattice degrees of freedom. Given the dynamic nature of the field, we chose to focus mainly on reviewing the experimental data, as on the experimental side a general consensus has been reached, whereas interpretations and related theoretical models can vary significantly. The first part of the paper introduces photoemission spectroscopy in the context of strongly interacting systems, along with an update on the state-of-the-art instrumentation. The second part provides an overview of the scientific issues relevant to the investigation of the low-energy electronic structure by ARPES. The rest of the paper is devoted to the experimental results from the cuprates, and the discussion is organized along conceptual lines: normal-state electronic structure, interlayer interaction, superconducting gap, coherent superconducting peak, pseudogap, electron self-energy, and collective modes. Within each topic, ARPES data from the various copper oxides are presented.

3,077 citations


Cites background from "Superconductivity at 93 K in a new ..."

  • ...F. YBa2Cu3O72d The Y-based copper oxides are probably the most important family of high-Tc superconductors....

    [...]

  • ...Depending on the number N of CuO2 planes contained within the characteristic blocks (N is also the number of Cu ions per formula unit), the cuprates are classified into single-layer compounds [e.g., LSCO, Bi2Sr2CuO61d , Nd22xCexCuO4 , and (Sr,Ca)2CuO2Cl2], bilayer compounds (e.g., Bi2Sr2CaCu2O81d and YBa2Cu3O72d), and trilayer compounds (e.g., Bi2Sr2Ca2Cu3O101d)....

    [...]

  • ...By 1987, a Tc of approximately 90 K (i.e., higher than the boiling point of liquid nitrogen at 77 K) was already observed in YBa2Cu3O72d (Wu et al., 1987)....

    [...]

  • ...In fact YBa2Cu3O72d (Y123) was the first compound for which superconductivity with Tc.77 K (i.e., the liquidnitrogen boiling point) was discovered (Wu et al., 1987)....

    [...]

  • ...Summary 504 D. Bi2Sr2CuO61d 504 E. Bi2Sr2Ca2Cu3O101d 505 F. YBa2Cu3O72d 505 G. Nd22xCexCuO4 507 H. Discussion 509 V. Superconducting Gap 510 A. Bi2Sr2CaCu2O81d 510 B. Bi2Sr2CuO61d 511 C. Bi2Sr2Ca2Cu3O101d 511 D. La22xSrxCuO4 511 E. YBa2Cu3O72d 512 F. Nd22xCexCuO4 512 G. Discussion 513 VI. Superconducting Peak 514 A. Bi2Sr2CaCu2O81d 514 B. Bi2Sr2Ca2Cu3O101d and Bi2Sr2CuO61d 517 VII....

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Journal ArticleDOI
TL;DR: In this paper, a new high-Tc oxide superconductor of the BiSrCa-Cu-O system without any rare earth element was discovered, which has Tc of about 105 K, higher than that of YBa2Cu3O7 by more than 10 K.
Abstract: We have discovered a new high-Tc oxide superconductor of the Bi-Sr-Ca-Cu-O system without any rare earth element. The oxide BiSrCaCu2Ox has Tc of about 105 K, higher than that of YBa2Cu3O7 by more than 10 K. In this oxide, the coexistence of Sr and Ca is necessary to obtain high Tc.

2,698 citations

Journal ArticleDOI
TL;DR: The observation of superconductivity with zero-resistance transition temperature at 8 K in the PbO-type α-FeSe compound is reported, indicating that this compound has the same, perhaps simpler, planar crystal sublattice as the layered oxypnictides.
Abstract: The recent discovery of superconductivity with relatively high transition temperature (Tc) in the layered iron-based quaternary oxypnictides La[O1−xFx] FeAs by Kamihara et al. [Kamihara Y, Watanabe T, Hirano M, Hosono H (2008) Iron-based layered superconductor La[O1-xFx] FeAs (x = 0.05–0.12) with Tc = 26 K. J Am Chem Soc 130:3296–3297.] was a real surprise and has generated tremendous interest. Although superconductivity exists in alloy that contains the element Fe, LaOMPn (with M = Fe, Ni; and Pn = P and As) is the first system where Fe plays the key role to the occurrence of superconductivity. LaOMPn has a layered crystal structure with an Fe-based plane. It is quite natural to search whether there exists other Fe based planar compounds that exhibit superconductivity. Here, we report the observation of superconductivity with zero-resistance transition temperature at 8 K in the PbO-type α-FeSe compound. A key observation is that the clean superconducting phase exists only in those samples prepared with intentional Se deficiency. FeSe, compared with LaOFeAs, is less toxic and much easier to handle. What is truly striking is that this compound has the same, perhaps simpler, planar crystal sublattice as the layered oxypnictides. Therefore, this result provides an opportunity to better understand the underlying mechanism of superconductivity in this class of unconventional superconductors.

2,544 citations


Cites background from "Superconductivity at 93 K in a new ..."

  • ...Unlike the high-temperature (high-Tc) superconductors (12) discovered 20 years ago that have a CuO2 plane that is essential for the observed superconductivity, the tetragonal phase -FeSe with PbO structure has an Fe-based planar sublattice equivalent to the layered iron-based quaternary oxypnictides, which have a layered crystal structure belonging to the P4/nmm space group (2)....

    [...]

Posted Content
TL;DR: In this article, Anderson's idea of the resonating valence bond (RVB) was introduced to describe the spin liquid phase of the undoped Mott insulator, and the slave-boson is introduced to enforce the constraint of no double occupation.
Abstract: This article reviews the effort to understand the physics of high temperature superconductors from the point of view of doping a Mott insulator. The basic electronic structure of the cuprates is reviewed, emphasizing the physics of strong correlation and establishing the model of a doped Mott insulator as a starting point. A variety of experiments are discussed, focusing on the region of the phase diagram close to the Mott insulator (the underdoped region) where the behavior is most anomalous. We introduce Anderson's idea of the resonating valence bond (RVB) and argue that it gives a qualitative account of the data. The importance of phase fluctuation is discussed, leading to a theory of the transition temperature which is driven by phase fluctuation and thermal excitation of quasiparticles. We then describe the numerical method of projected wavefunction which turns out to be a very useful technique to implement the strong correlation constraint, and leads to a number of predictions which are in agreement with experiments. The remainder of the paper deals with an analytic treatment of the t-J model, with the goal of putting the RVB idea on a more formal footing. The slave-boson is introduced to enforce the constraint of no double occupation. The implementation of the local constraint leads naturally to gauge theories. We give a rather thorough discussion of the role of gauge theory in describing the spin liquid phase of the undoped Mott insulator. We next describe the extension of the SU(2) formulation to nonzero doping. We show that inclusion of gauge fluctuation provides a reasonable description of the pseudogap phase.

2,042 citations

References
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Journal ArticleDOI
TL;DR: In this paper, Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form, and samples with x=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound.
Abstract: Metallic, oxygen-deficient compounds in the Ba−La−Cu−O system, with the composition BaxLa5−xCu5O5(3−y) have been prepared in polycrystalline form. Samples withx=1 and 0.75,y>0, annealed below 900°C under reducing conditions, consist of three phases, one of them a perovskite-like mixed-valent copper compound. Upon cooling, the samples show a linear decrease in resistivity, then an approximately logarithmic increase, interpreted as a beginning of localization. Finally an abrupt decrease by up to three orders of magnitude occurs, reminiscent of the onset of percolative superconductivity. The highest onset temperature is observed in the 30 K range. It is markedly reduced by high current densities. Thus, it results partially from the percolative nature, bute possibly also from 2D superconducting fluctuations of double perovskite layers of one of the phases present.

10,272 citations

Journal ArticleDOI
Ching-Wu Chu1, Pei-Herng Hor1, R. L. Meng1, Li Gao1, Z. J. Huang1, and Y. Q. Wang1 
TL;DR: An apparent superconducting transition with an onset temperature above 40 K has been detected under pressures in the La-Ba-Cu-O compound system synthesized directly from a solid-state reaction of La/sub 2/O/ sub 3/, CuO, and BaCO/sub 3/ followed by a decomposition of the mixture in a reduced atmosphere.
Abstract: An apparent superconducting transition with an onset temperature above 40 K has been detected under pressure in the La-Ba-Cu-O compound system synthesized directly from a solid-state reaction of La2O3, CuO, and BaCO3 followed by a decomposition of the mixture in a reduced atmosphere. The experiment is described and the results of effects of magnetic field and pressure are discussed.

1,128 citations

Journal ArticleDOI
TL;DR: The results of resistivity and magnetic susceptibility measurements in La/sub 2-//sub x/Sr/sub X/CuO/sub 4/ for x less than or equal to 0.3 were reported in this article.
Abstract: We report the results of resistivity and magnetic susceptibility measurements in La/sub 2-//sub x/Sr/sub x/CuO/sub 4/ for xless than or equal to0.3. The x = 0.2 sample shows a superconducting transition at 36.2 K with a width of 1.4 K. The associated dc diamagnetic susceptibility (Meissner effect) is a large fraction (60%--70%) of the ideal value. We estimate the density of states from critical-field and resistivity data and suggest, by analogy to BaPb/sub 1-//sub x/Bi/sub x/O/sub 3/, that conventional phonon-mediated superconductivity can account for the high T/sub c/ in this class of materials.

784 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that Niobium-germanium (Nb3Ge) superconducting up to 22.3 K can be obtained by a high pressure dc sputtering process.
Abstract: Niobium‐germanium films which remain superconducting up to 22.3 K have been prepared by a high‐pressure dc sputtering process. The high Tc's of these films are attributed to the formation of a more nearly perfect stoichiometric Nb3Ge compound than has previously been obtainable.

345 citations

Journal ArticleDOI
TL;DR: In this paper, a broad superconducting transition with an onset near 30 K was observed for La-Ba-Cu oxides in the measurement of magnetic susceptibility, which is of bulk nature and reproducible after several heat cycles.
Abstract: A broad superconducting transition with an onset near 30 K is observed for La-Ba-Cu oxides in the measurement of magnetic susceptibility. The superconductivity is of bulk nature and reproducible after several heat cycles.

257 citations