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Sample records for earth re123 cuprate

  1. Heat capacity of rare-earth cuprates, orthovanadates, and aluminum garnets, gallium garnets, and iron garnets

    NASA Astrophysics Data System (ADS)

    Denisova, L. T.; Kargin, Yu. F.; Denisov, V. M.

    2015-08-01

    The correlation between the heat capacities of rare-earth cuprates, orthovanadates, and garnets with ionic radius R 3+ has been analyzed. It has been shown that the values of C {/p 0} change consistently depending on the radius R 3+ within the corresponding tetrads (La-Nd, Pm-Gd, Gd-Ho, Eu-Lu).

  2. Sample and length-dependent variability of 77 and 4.2 K properties in nominally identical RE123 coated conductors

    NASA Astrophysics Data System (ADS)

    Rossi, L.; Hu, X.; Kametani, F.; Abraimov, D.; Polyanskii, A.; Jaroszynski, J.; Larbalestier, D. C.

    2016-05-01

    We present a broad study by multiple techniques of the critical current and critical current density of a small but representative set of nominally identical commercial RE123 (REBa2Cu3O7-δ , RE = rare Earth, here Y and Gd) coated conductors (CC) recently fabricated by SuperPower Inc. to the same nominal high pinning specification with BaZrO3 and RE2O3 nanoprecipitate pinning centers. With high-field low-temperature applications to magnet technology in mind, we address the nature of their tape-to-tape variations and length-wise I c inhomogeneities by measurements on a scale of about 2 cm rather than the 5 m scale normally supplied by the vendor and address the question of whether these variations have their origin in cross-sectional or in vortex pinning variations. Our principal method has been a continuous measurement transport critical current tool (YateStar) that applies about 0.5 T perpendicular and parallel to the tape at 77 K, thus allowing variations of c-axis and ab-plane properties to be clearly distinguished in the temperature and field regime where strong pinning defects are obvious. We also find such in-field measurements at 77 K to be more valuable in predicting 4.2 K, high-field properties than self-field, 77 K properties because the pinning centers controlling 77 K performance play a decisive role in introducing point defects that also add strongly to J c at 4.2 K. We find that the dominant source of I c variation is due to pinning center fluctuations that control J c, rather than to production defects that locally reduce the active cross-section. Given the 5-10 nm scale of these pinning centers, it appears that the route to greater I c homogeneity is through more stringent control of the REBCO growth conditions in these Zr-doped coated conductors.

  3. Coupling of the orthorhombic distortion to the depression of the {Tc}`s due to Zn{sup 2+} doping in the ``RE-123`` HTSC`s: A (d + s)-wave picture

    SciTech Connect

    Tang, I.M.; Thongruang, R.; Charoenthai, N.

    1999-07-10

    The depressions of the {Tc}`s of the 123 REBa{sub 2}Cu{sub 3}O{sub 7} HTSC`s due to the substitution of Zn{sup 2+} ions into the Cu(2) layer are studied. The orthorhombic distortion which occurs in the 123 ceramics is assumed to induce a modification to the spin-fluctuation (SF) mediated pairing interaction which in turn causes the order parameters of these HTSC`s to be of mixed (d + s)-wave symmetry. It is shown that part of the rapid depression of the {Tc}`s caused by Zn{sup 2+} substitution into the CuO{sup 2} is due to a reduction of the SF-mediated pairing interaction. The differences in the rates of suppression of {Tc} due to Zn{sup 2+} doping in the different RE-123 HTSC`s are shown to be due to the changes in the orthorhombicity which depend on the size of the rare earth ions.

  4. Direct cupration of fluoroform.

    PubMed

    Zanardi, Alessandro; Novikov, Maxim A; Martin, Eddy; Benet-Buchholz, Jordi; Grushin, Vladimir V

    2011-12-28

    We have found the first reaction of direct cupration of fluoroform, the most attractive CF(3) source for the introduction of the trifluoromethyl group into organic molecules. Treatment of CuX (X = Cl, Br, I) with 2 equiv of MOR (M = K, Na) in DMF or NMP produces novel alkoxycuprates that readily react with CF(3)H at room temperature and atmospheric pressure to give CuCF(3) derivatives. The CuCl and t-BuOK (1:2) combination provides best results, furnishing the CuCF(3) product within seconds in nearly quantitative yield. As demonstrated, neither CF(3)(-) nor CF(2) mediate the Cu-CF(3) bond formation, which accounts for its remarkably high selectivity. The fluoroform-derived CuCF(3) solutions can be efficiently stabilized with TREAT HF to produce CuCF(3) reagents that readily trifluoromethylate organic and inorganic electrophiles in the absence of additional ligands such as phenanthroline. A series of novel Cu(I) complexes have been structurally characterized, including K(DMF)[Cu(OBu-t)(2)] (1), Na(DMF)(2)[Cu(OBu-t)(2)] (2), [K(8)Cu(6)(OBu-t)(12)(DMF)(8)(I)](+) I(-) (3), and [Cu(4)(CF(3))(2)(C(OBu-t)(2))(2)(μ(3)-OBu-t)(2)] (7). PMID:22136628

  5. Raman scattering in cuprate superconductors

    SciTech Connect

    Devereaux, T.P.; Kampf, A.P.

    1997-07-20

    A theory for electronic Raman scattering in the cuprate superconductors is presented with a specific emphasis on the polarization dependence of the spectra which can infer the symmetry of the energy gap. Signatures of the effects of disorder on the low frequency and low temperature behavior of the Raman spectra for different symmetry channels provide detailed information about the magnitude and the phase of the energy gap. Properties of the theory for finite T will be discussed and compared to recent data concerning the doping dependence of the Raman spectra in cuprate superconductors, and remaining questions will be addressed.

  6. Earth

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1984-01-01

    The following aspects of the planet Earth are discussed: plate tectonics, the interior of the planet, the formation of the Earth, and the evolution of the atmosphere and hydrosphere. The Earth's crust, mantle, and core are examined along with the bulk composition of the planet.

  7. Oxygen diffusion in cuprate superconductors

    SciTech Connect

    Routbort, J.L.; Rothman, S.J.

    1995-01-01

    Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La{sub 2}{sub {minus}}{sub {times}}Sr{sub {times}}CuO{sub 4}, YBa{sub 2}Cu{sub 3}O{sub 7}{sub {minus}}{delta}, YBa{sub 2}Cu{sub 4}O{sub 8}, and the Bi{sub 2}Sr{sub 2}Ca{sub n}{sub {minus}}{sub 1}Cu{sub n}O{sub 2}{sub +}{sub 4} (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible.

  8. Chasing arcs in cuprate superconductors.

    SciTech Connect

    Norman, M. R.; Materials Science Division

    2009-01-01

    Important clues to the origin of high-temperature superconductivity in cuprate compounds lie within the normal phase of these compounds, which forms above the transition temperature T{sub c}. One unusual feature of the normal phase is the presence of a pseudogap; depending on the momentum of the charge carrier, its excitation energy is either zero or finite (1). Two reports in Science, by Pushp et al. (2) in June and by Lee et al. (3) on page 1099 of this issue, have used scanning tunneling microscopy to provide dramatic new insights into the pseudogap phase and to elucidate how the electronic excitations, both above and below T{sub c}, differ for different values of the carrier momentum.

  9. The color of polarization in cuprate superconductors

    NASA Technical Reports Server (NTRS)

    Hoff, H. A.; Osofsky, M. S.; Lechter, W. L.; Pande, C. S.

    1991-01-01

    A technique for the identification of individual anisotropic grains in a heterogeneous and opaque material involves the observation of grain color in reflected light through crossed polarizers (color of polarization). Such colors are generally characteristic of particular phases. When grains of many members of the class of hole carrier cuprate superconductors are so viewed at room temperature with a 'daylight' source, a characteristic color of polarization is observed. This color was studied in many of these cuprate superconductors and a strong correlation was found between color and the existence of superconductivity. Two members were also examined of the electron cuprate superconductors and it was found that they possess the same color of polarization as the hole carrier cuprate superconductors so far examined. The commonality of the characteristic color regardless of charge carrier indicates that the presence of this color is independent of carrier type. The correlation of this color with the existence of superconductivity in the cuprate superconductors suggests that the origin of the color relates to the origin of superconductivity. Photometric techniques are also discussed.

  10. Lattice, spin, and charge excitations in cuprates

    NASA Astrophysics Data System (ADS)

    Lee, Wei-Sheng

    2014-03-01

    Tracking doping evolution of elementary excitations is a crucial approach to understand the complex phenomena exhibited in cuprates. In the first part of my talk, I will discuss the role of the lattice in the quasi-one-dimensional edge-sharing cuprate Y2+xCa2-xCu5O10. Using O K-edge RIXS, we resolve site-dependent harmonic phonon excitations of a 70 meV mode. Coupled with theory, this provides a direct measurement of electron-lattice coupling strength. We show that such electron-lattice coupling causes doping-dependent distortions of the Cu-O-Cu bond angle, which sets the intra-chain spin exchange interactions. In the second part of my talk, I will discuss collective excitations in the electron-doped superconducting cuprate, Nd2-xCexCuO4 observed using Cu L-edge RIXS. Surprisingly, despite the fact that the spin stiffness is zero and the AFM correlations are short-ranged, magnetic excitations harden significantly across the AFM-HTSC phase boundary, in stark contrast with the hole-doped cuprates. Furthermore, we found an unexpected and highly dispersive mode emanating from the zone center in superconducting NCCO that is undetected in the hole-doped compounds. This may signal a quantum phase distinct from superconductivity. Thus, our results indicate an asymmetry of the collective excitations in electron- and hole-doped cuprates, providing a new perspective on the doping evolution of the cuprate ground state. This work is supported by DOE Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract DE-AC02-76SF00515.

  11. Enhancing critical current density of cuprate superconductors

    DOEpatents

    Chaudhari, Praveen

    2015-06-16

    The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.

  12. Excess Oxygen Defects in Layered Cuprates

    DOE R&D Accomplishments Database

    Lightfoot, P.; Pei, S. Y.; Jorgensen, J. D.; Manthiram, A.; Tang, X. X.; Goodenough, J. B.

    1990-09-01

    Neutron powder diffraction has been used to study the oxygen defect chemistry of two non-superconducting layered cuprates, La{sub 1. 25}Dy{sub 0.75}Cu{sub 3.75}F{sub 0.5}, having a T{sup {asterisk}}- related structure, and La{sub 1.85}Sr{sub 1.15}Cu{sub 2}O{sub 6.25}, having a structure related to that of the newly discovered double-layer superconductor La{sub 2-x}Sr{sub x}CaCu{sub 2}O{sub 6}. The role played by oxygen defects in determining the superconducting properties of layered cuprates is discussed.

  13. Impurity induced resistivity upturns in underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Das, Nabyendu; Singh, Navinder

    2016-01-01

    Impurity induced low temperature upturns in both the ab-plane and the c-axis dc-resistivities of cuprates in the pseudogap state have been observed in experiments. We provide an explanation of this phenomenon by incorporating impurity scattering of the charge carriers within a phenomenological model proposed by Yang, Rice and Zhang. The scattering between charge carriers and the impurity atom is considered within the lowest order Born approximation. Resistivity is calculated within Kubo formula using the impurity renormalized spectral functions. Using physical parameters for cuprates, we describe qualitative features of the upturn phenomena and its doping evolution that coincides with the experimental findings. We stress that this effect is largely due to the strong electronic correlations.

  14. Hole-doped cuprate high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Chu, C. W.; Deng, L. Z.; Lv, B.

    2015-07-01

    Hole-doped cuprate high temperature superconductors have ushered in the modern era of high temperature superconductivity (HTS) and have continued to be at center stage in the field. Extensive studies have been made, many compounds discovered, voluminous data compiled, numerous models proposed, many review articles written, and various prototype devices made and tested with better performance than their nonsuperconducting counterparts. The field is indeed vast. We have therefore decided to focus on the major cuprate materials systems that have laid the foundation of HTS science and technology and present several simple scaling laws that show the systematic and universal simplicity amid the complexity of these material systems, while referring readers interested in the HTS physics and devices to the review articles. Developments in the field are mostly presented in chronological order, sometimes with anecdotes, in an attempt to share some of the moments of excitement and despair in the history of HTS with readers, especially the younger ones.

  15. Sequential imposed layer epitaxy of cuprate films

    SciTech Connect

    Laguees, M.; Tebbji, H.; Mairet, V.; Hatterer, C.; Beuran, C.F.; Hass, N.; Xu, X.Z. ); Cavellin, C.D. )

    1994-02-01

    Layer-by-layer epitaxy has been used to grow cuprate films since the discovery of high-Tc compounds. This deposition technique is in principle suitable for the growth of layered crystalline structures. However, the sequential deposition of atomic layer by atomic layer of cuprate compounds has presently not been optimized. Nevertheless, this deposition process is the only one which allows one to build artificial cell structures such as Bi[sub 2]Sr[sub 2]Ca[sub (n[minus]1)]Cu[sub n]O[sub y] with n as large as 10. This process will also be the best one to grow films of the so-called infinite layer phase compounds belonging to the Sr[sub 1[minus]x]Ca[sub x]CuO[sub 2] family, in order to improve the transport properties and the morphological properties of the cuprate films. When performed at high substrate temperature (typically more than 600[degree]C), the layer-by-layer epitaxy of cuprates exhibits usually 3D aggregate nucleation. Then the growth of the film no longer obeys the layer-by-layer sequence imposed during the deposition. We present here two experimental situations of true 2D sequential imposed layer epitaxy; the growth at 500[degree]C under atomic oxygen pressure of Bi[sub 2]Sr[sub 2]CuO[sub 6] and of Sr[sub 1[minus]x]Ca[sub y]CuO[sub 2] phases. 20 refs., 2 figs.

  16. Quasiparticle tunneling spectroscopy of high {Tc} cuprates

    SciTech Connect

    Zasadzinski, J.; Ozyuzer, L.; Yusof, Z.; Chen, J.; Gray, K.E.; Mogilevsky, R.; Hinks, D.G.; Cobb, J.L.; Markert, J.T.

    1996-04-01

    Superconductor-insulator-normal metal (SIN) and superconductor-insulator-superconductor (SIS) tunnel junctions provide important information on pairing state symmetry and mechanism. Measurements of such junctions on high {Tc} superconductors (HTS) are reported using mechanical point contacts, which generally display the optimum characteristics that can be obtained from HTS native-surface tunnel barriers. New tunneling data on the infinite-layer cuprate, Sr{sub 1{minus}x}Nd{sub x}CuO{sub 2} are reported which show a remarkable similarity to another electron-doped cuprate, Nd{sub 1.85}Ce{sub 0.85}CuO{sub 4}. In particular, there is a strong, asymmetric linear background conductance that is indicative of inelastic tunneling from a continuum of states. A discussion is given of the anomalous dip feature found in the tunneling and photoemission data on BSCCO 2212. It is shown that a similar feature is found in many cuprate junctions and that this dip scales with the gap energy over a wide range. New data on the single-layer, tetragonal cuprate, Tl{sub 2}Ba{sub 2}CuO{sub 6} (Tl2201) are presented and discussed in light of recent published results on the similar compound HgBa{sub 2}CuO{sub 4} (Hg1201). The HG1201 data display a low, flat sub-gap tunneling conductance which is consistent with a BCS density of states whereas the T12201 data display a cusp-like feature at zero bias which is more consistent with d{sub x}2-{sub y}2 symmetry.

  17. Ferroelectricity in underdoped La-based cuprates.

    PubMed

    Viskadourakis, Z; Sunku, S S; Mukherjee, S; Andersen, B M; Ito, T; Sasagawa, T; Panagopoulos, C

    2015-01-01

    Doping a "parent" antiferromagnetic Mott insulator in cuprates leads to short-range electronic correlations and eventually to high-Tc superconductivity. However, the nature of charge correlations in the lightly doped cuprates remains unclear. Understanding the intermediate electronic phase in the phase diagram (between the parent insulator and the high-Tc superconductor) is expected to elucidate the complexity both inside and outside the superconducting dome, and in particular in the underdoped region. One such phase is ferroelectricity whose origin and relation to the properties of high-Tc superconductors is subject of current research. Here we demonstrate that ferroelectricity and the associated magnetoelectric coupling are in fact common in La-214 cuprates namely, La2-xSrxCuO4, La2LixCu1-xO4 and La2CuO4+x. It is proposed that ferroelectricity may result from local CuO6 octahedral distortions, associated with the dopant atoms and clustering of the doped charge carriers, which break spatial inversion symmetry at the local scale whereas magnetoelectric coupling can be tuned through Dzyaloshinskii-Moriya interaction. PMID:26486276

  18. Symmetry of charge order in cuprates

    NASA Astrophysics Data System (ADS)

    Comin, R.; Sutarto, R.; He, F.; da Silva Neto, E. H.; Chauviere, L.; Fraño, A.; Liang, R.; Hardy, W. N.; Bonn, D. A.; Yoshida, Y.; Eisaki, H.; Achkar, A. J.; Hawthorn, D. G.; Keimer, B.; Sawatzky, G. A.; Damascelli, A.

    2015-08-01

    Charge-ordered ground states permeate the phenomenology of 3d-based transition metal oxides, and more generally represent a distinctive hallmark of strongly correlated states of matter. The recent discovery of charge order in various cuprate families has fuelled new interest into the role played by this incipient broken symmetry within the complex phase diagram of high-Tc superconductors. Here, we use resonant X-ray scattering to resolve the main characteristics of the charge-modulated state in two cuprate families: Bi2Sr2-xLaxCuO6+δ (Bi2201) and YBa2Cu3O6+y (YBCO). We detect no signatures of spatial modulations along the nodal direction in Bi2201, thus clarifying the inter-unit-cell momentum structure of charge order. We also resolve the intra-unit-cell symmetry of the charge-ordered state, which is revealed to be best represented by a bond order with modulated charges on the O-2p orbitals and a prominent d-wave character. These results provide insights into the origin and microscopic description of charge order in cuprates, and its interplay with superconductivity.

  19. Ferroelectricity in underdoped La-based cuprates

    PubMed Central

    Viskadourakis, Z.; Sunku, S. S.; Mukherjee, S.; Andersen, B. M.; Ito, T.; Sasagawa, T.; Panagopoulos, C.

    2015-01-01

    Doping a “parent” antiferromagnetic Mott insulator in cuprates leads to short-range electronic correlations and eventually to high-Tc superconductivity. However, the nature of charge correlations in the lightly doped cuprates remains unclear. Understanding the intermediate electronic phase in the phase diagram (between the parent insulator and the high-Tc superconductor) is expected to elucidate the complexity both inside and outside the superconducting dome, and in particular in the underdoped region. One such phase is ferroelectricity whose origin and relation to the properties of high-Tc superconductors is subject of current research. Here we demonstrate that ferroelectricity and the associated magnetoelectric coupling are in fact common in La-214 cuprates namely, La2-xSrxCuO4, La2LixCu1-xO4 and La2CuO4+x. It is proposed that ferroelectricity may result from local CuO6 octahedral distortions, associated with the dopant atoms and clustering of the doped charge carriers, which break spatial inversion symmetry at the local scale whereas magnetoelectric coupling can be tuned through Dzyaloshinskii-Moriya interaction. PMID:26486276

  20. Symmetry of charge order in cuprates.

    PubMed

    Comin, R; Sutarto, R; He, F; da Silva Neto, E H; Chauviere, L; Fraño, A; Liang, R; Hardy, W N; Bonn, D A; Yoshida, Y; Eisaki, H; Achkar, A J; Hawthorn, D G; Keimer, B; Sawatzky, G A; Damascelli, A

    2015-08-01

    Charge-ordered ground states permeate the phenomenology of 3d-based transition metal oxides, and more generally represent a distinctive hallmark of strongly correlated states of matter. The recent discovery of charge order in various cuprate families has fuelled new interest into the role played by this incipient broken symmetry within the complex phase diagram of high-T(c) superconductors. Here, we use resonant X-ray scattering to resolve the main characteristics of the charge-modulated state in two cuprate families: Bi2Sr(2-x)La(x)CuO(6+δ) (Bi2201) and YBa2Cu3O(6+y) (YBCO). We detect no signatures of spatial modulations along the nodal direction in Bi2201, thus clarifying the inter-unit-cell momentum structure of charge order. We also resolve the intra-unit-cell symmetry of the charge-ordered state, which is revealed to be best represented by a bond order with modulated charges on the O-2p orbitals and a prominent d-wave character. These results provide insights into the origin and microscopic description of charge order in cuprates, and its interplay with superconductivity. PMID:26006005

  1. Enhanced pinning in mixed rare earth-123 films

    SciTech Connect

    Driscoll, Judith L.; Foltyn, Stephen R.

    2009-06-16

    An superconductive article and method of forming such an article is disclosed, the article including a substrate and a layer of a rare earth barium cuprate film upon the substrate, the rare earth barium cuprate film including two or more rare earth metals capable of yielding a superconductive composition where ion size variance between the two or more rare earth metals is characterized as greater than zero and less than about 10.times.10.sup.-4, and the rare earth barium cuprate film including two or more rare earth metals is further characterized as having an enhanced critical current density in comparison to a standard YBa.sub.2Cu.sub.3O.sub.y composition under identical testing conditions.

  2. Sr2IrO4: Gateway to cuprate superconductivity?

    DOE PAGESBeta

    Mitchell, J. F.

    2015-06-05

    High temperature superconductivity in cuprates remains a defining challenge in condensed matter physics. Recently, a new set of related compounds based on Ir rather than Cu has been discovered that may be on the verge of superconductivity themselves or be able to shed new light on the underlying interactions responsible for superconductivity in the cuprates.

  3. Chasing the cuprates with dilatonic dyons

    NASA Astrophysics Data System (ADS)

    Amoretti, Andrea; Baggioli, Matteo; Magnoli, Nicodemo; Musso, Daniele

    2016-06-01

    Magnetic field and momentum dissipation are key ingredients in describing condensed matter systems. We include them in gauge/gravity and systematically explore the bottom-up panorama of holographic IR effective field theories based on bulk EinsteinMaxwell Lagrangians plus scalars. The class of solutions here examined appears insufficient to capture the phenomenology of charge transport in the cuprates. We analyze in particular the temperature scaling of the resistivity and of the Hall angle. Keeping an open attitude, we illustrate weak and strong points of the approach.

  4. μSR Studies of Cuprate Superconductors

    NASA Astrophysics Data System (ADS)

    Sonier, Jeff E.

    2016-09-01

    A partial review of magnetic and superconducting properties of hole-doped cuprates determined by μSR is given. Much was learned about these materials from μSR experiments performed in the early years following the discovery of high-temperature superconductivity over an intermediate range of hole doping. Through the years improvements in sample quality and μSR instrumentation has led to new information and a refined understanding of the superconductivity and magnetism. Implicit in the discussion is the evolution of the superconducting and magnetic order parameters as a function of doping concentration, temperature and magnetic field, as evidenced by μSR.

  5. Universality in Cuprates: A Gauge Approach

    NASA Astrophysics Data System (ADS)

    Marchetti, P. A.; Bighin, G.

    2016-05-01

    In high-T_c cuprates, many quantities exhibit a non-Fermi liquid universality hinting at a very peculiar structure of the underlying pairing mechanism for superconductivity: in this work, we focus on the universality for the in-plane resistivity and the superfluid density. We outline the previously developed spin-charge gauge approach to superconductivity in hole-doped cuprates: we decompose the hole of the t-t'-J model for the CuO_2 planes as the product of a spinful, chargeless gapped spinon and a spinless, charged holon with Fermi surface. Each one of these particle excitations is bound to a statistical gauge flux, allowing one to optimize their statistics. We show that this model allows for a natural interpretation of the universality: within this approach, under suitable conditions, the spinonic and holonic contributions to a response function sum up according to the Ioffe-Larkin rule. We argue that, if the spinonic contribution dominates, then one should expect strongly non-Fermi-liquid-like universality, due to the insensitivity of spinons to Fermi surface details. The in-plane resistivity and superfluid density are indeed dominated by spinons in the underdoped region. We theoretically derive these quantities, discussing their universal behaviours and comparing them with experimental data.

  6. Theory of nonequilibrium superconductivity in cuprates

    NASA Astrophysics Data System (ADS)

    Oka, Takashi; Pietilä, Ville

    2013-03-01

    Recently, nonequilibrium properties of Hi Tc superconductors are attracting much interest. This is because new experimental methods such as time resolved ARPES has been applied to cuprates and succeeded in observing the dynamics of photo-excited quasiparticles as well as the temporal evolution of the d-wave superconducting order parameter (e.g.,). One can also realize nonequilibrium states in interfaces between cuprates and metal electrodes and control the superconducting order by changing the applied bias. In order to study the dynamics of superconductivity in strongly correlated systems, we developed a novel numerical method by combining the quantum kinetic equation with the fluctuation exchange approximation (FLEX, self-consistent T-matrix approximation). This method enables us to study the interplay between pair mediating fluctuations, e.g., antiferromagnetic and charge fluctuations, and the dynamics of quasiparticles and superconducting order parameter. In the presentation, we explain the physical insights we obtain by applying this method to nonequilibrium dynamics in d-wave superconductors.

  7. Unparticles and anomalous dimensions in the cuprates

    NASA Astrophysics Data System (ADS)

    Karch, Andreas; Limtragool, Kridsanaphong; Phillips, Philip W.

    2016-03-01

    Motivated by the overwhelming evidence some type of quantum criticality underlies the power-law for the optical conductivity and T-linear resistivity in the cuprates, we demonstrate here how a scale-invariant or unparticle sector can lead to a unifying description of the observed scaling forms. We adopt the continuous mass formalism or multi band (flavor) formalism of the unparticle sector by letting various microscopic parameters be mass-dependent. In particular, we show that an effective mass that varies with the flavor index as well as a running band edge and lifetime capture the AC and DC transport phenomenology of the cuprates. A key consequence of the running mass is that the effective dynamical exponent can differ from the underlying bare critical exponent, thereby providing a mechanism for realizing the fractional values of the dynamical exponent required in a previous analysis [1]. We also predict that regardless of the bare dynamical exponent, z, a non-zero anomalous dimension for the current is required. Physically, the anomalous dimension arises because the charge depends on the flavor, mass or energy. The equivalent phenomenon in a d + 1 gravitational construction is the running of the charge along the radial direction. The nature of the superconducting instability in the presence of scale invariant stuff shows that the transition temperature is not necessarily a monotonic function of the pairing interaction.

  8. Superconductivity and planar hole densities in the cuprates from NMR

    NASA Astrophysics Data System (ADS)

    Haase, Juergen; Jurkutat, Michael; Rybicki, Damian

    We show how nuclear magnetic resonance (NMR) of 63Cu and 17O provides a quantitative measure of the charge distribution in the ubiquitous CuO2 plane, the common structural feature of cuprate physics. The various materials are found to differ significantly in the local charge distribution, while the total charge per CuO2 matches expectation from stoichiometry. Using the local charges on Cu and O measured by NMR, a new three-dimensional cuprate phase diagram is drawn that consistently encompasses all cuprate materials. These appear ordered according to their maximum Tc. It is the sharing of the inherent Cu hole with O that sets an upper limit for Tc, and it correlates with the superfluid density measured by μSR, over all cuprate families.

  9. Charge-transfer gap and superexchange interaction in insulating cuprates

    SciTech Connect

    Ohta, Y.; Tohyama, T.; Maekawa, S. )

    1991-03-04

    A cluster-model analysis is made on the material dependence of the optical charge-transfer gap and antiferromagnetic superexchange interaction of a variety of insulating cuprates. It is shown that the electronic structure of cuprates typically of the charge-transfer type is characterized by the unique energy-level separation that reflects the three dimensionality of the crystal via the long-range Madelung potential; such characteristics are absent in the Mott-Hubbard regime.

  10. Two band model for the cuprates

    NASA Astrophysics Data System (ADS)

    Liu, Shiu; White, Steven

    2009-03-01

    We use a numerical canonical transformation approach to derive an effective two-band model for the hole-doped cuprates, which keeps both oxygen and copper orbitals but removes double occupancy from each. A similar model was considered previously by Frenkel, Gooding, Shraiman, and Siggia (PRB 41, number 1, page 350). We compare the numerically derived model with previously obtained analytical results. In addition to the usual hopping terms between oxygens tpp and Cu-Cu exchange terms Jdd, the model also includes a strong copper-oxygen exchange interaction Jpd and a Kondo-like spin-flip oxygen-oxygen hopping term Kpdp. We use the density matrix renormalization group to study the charge, spin, and pairing properties of the derived model on ladder systems.

  11. Fermi surface anisotropy in the cuprates

    NASA Astrophysics Data System (ADS)

    Ramshaw, Brad

    Broken rotational (C4) symmetry is a distinguishing feature for a number of experiments in the underdoped high-Tc cuprates, including electrical resistivity, neutron scattering, Nernst coefficient, and scanning tunneling microscopy. This broken symmetry has not been observed on the Fermi surface, however, with or without the presence of an applied magnetic field. We measure the angle-dependent magnetoresistance-a quantity known to be extremely sensitive to the geometry and symmetry of the Fermi surface-of YBa2Cu3O6.58, and find that the Fermi surface has a clear two-fold symmetry, breaking the C4 symmetry of the copper-oxide plane. We discuss the implications of this finding, including how it fits with recent X-ray measurements in high magnetic fields.

  12. Antiferromagnetically Induced Photoemission Band in the Cuprates

    NASA Astrophysics Data System (ADS)

    Haas, Stephan; Moreo, Adriana; Dagotto, Elbio

    1995-05-01

    Strong antiferromagnetic correlations in models of high critical temperature (high- Tc) cuprates produce quasiparticlelike features in photoemission (PES) calculations above the Fermi momentum pF corresponding to weakly interacting electrons. This effect, discussed before by Kampf and Schrieffer [Phys. Rev. B 41, 6399 (1990)], is analyzed here using computational techniques in strong coupling. It is concluded that weight above pF should be observable in PES data for underdoped compounds, while in the overdoped regime it will be hidden in the experimental background. At optimal doping the signal is weak. The order of magnitude of our results is compatible with experimental data by Aebi et al. [Phys. Rev. Lett. 72, 2757 (1994)] for Bi2Sr2CaCu2O8.

  13. Pairing, pseudogap and Fermi arcs in cuprates

    SciTech Connect

    Kaminski, Adam; Kondo, Takeshi; Takeuchi, Tsunehiro; Gu, Genda

    2014-04-29

    We use Angle Resolved Photoemission Spectroscopy (ARPES) to study the relationship between the pseudogap, pairing and Fermi arcs in cuprates. High quality data measured over a wide range of dopings reveals a consistent picture of Fermiology and pairing in these materials. The pseudogap is due to an ordered state that competes with superconductivity rather than preformed pairs. Pairing does occur below Tpair ~ 150K and significantly above Tc, but well below T* and the doping dependence of this temperature scale is distinct from that of the pseudogap. The d-wave gap is present below Tpair, and its interplay with strong scattering creates “artificial” Fermi arcs for Tc ≤ T ≤ Tpair. However, above Tpair, the pseudogap exists only at the antipodal region. This leads to presence of real, gapless Fermi arcs close to the node. The length of these arcs remains constant up to T*, where the full Fermi surface is recovered. As a result, we demonstrate that these findings resolve a number of seemingly contradictory scenarios.

  14. Pairing, pseudogap and Fermi arcs in cuprates

    DOE PAGESBeta

    Kaminski, Adam; Kondo, Takeshi; Takeuchi, Tsunehiro; Gu, Genda

    2014-04-29

    We use Angle Resolved Photoemission Spectroscopy (ARPES) to study the relationship between the pseudogap, pairing and Fermi arcs in cuprates. High quality data measured over a wide range of dopings reveals a consistent picture of Fermiology and pairing in these materials. The pseudogap is due to an ordered state that competes with superconductivity rather than preformed pairs. Pairing does occur below Tpair ~ 150K and significantly above Tc, but well below T* and the doping dependence of this temperature scale is distinct from that of the pseudogap. The d-wave gap is present below Tpair, and its interplay with strong scatteringmore » creates “artificial” Fermi arcs for Tc ≤ T ≤ Tpair. However, above Tpair, the pseudogap exists only at the antipodal region. This leads to presence of real, gapless Fermi arcs close to the node. The length of these arcs remains constant up to T*, where the full Fermi surface is recovered. As a result, we demonstrate that these findings resolve a number of seemingly contradictory scenarios.« less

  15. Fermi-surface reconstruction by stripe order in cuprate superconductors

    PubMed Central

    Laliberté, F.; Chang, J.; Doiron-Leyraud, N.; Hassinger, E.; Daou, R.; Rondeau, M.; Ramshaw, B.J.; Liang, R.; Bonn, D.A.; Hardy, W.N.; Pyon, S.; Takayama, T.; Takagi, H.; Sheikin, I.; Malone, L.; Proust, C.; Behnia, K.; Taillefer, Louis

    2011-01-01

    The origin of pairing in a superconductor resides in the underlying normal state. In the cuprate high-temperature superconductor YBa2Cu3Oy (YBCO), application of a magnetic field to suppress superconductivity reveals a ground state that appears to break the translational symmetry of the lattice, pointing to some density-wave order. Here we use a comparative study of thermoelectric transport in the cuprates YBCO and La1.8−xEu0.2SrxCuO4 (Eu-LSCO) to show that the two materials exhibit the same process of Fermi-surface reconstruction as a function of temperature and doping. The fact that in Eu-LSCO this reconstruction coexists with spin and charge modulations that break translational symmetry shows that stripe order is the generic non-superconducting ground state of hole-doped cuprates. PMID:21847106

  16. Fermi-surface reconstruction by stripe order in cuprate superconductors.

    PubMed

    Laliberté, F; Chang, J; Doiron-Leyraud, N; Hassinger, E; Daou, R; Rondeau, M; Ramshaw, B J; Liang, R; Bonn, D A; Hardy, W N; Pyon, S; Takayama, T; Takagi, H; Sheikin, I; Malone, L; Proust, C; Behnia, K; Taillefer, Louis

    2011-01-01

    The origin of pairing in a superconductor resides in the underlying normal state. In the cuprate high-temperature superconductor YBa(2)Cu(3)O(y) (YBCO), application of a magnetic field to suppress superconductivity reveals a ground state that appears to break the translational symmetry of the lattice, pointing to some density-wave order. Here we use a comparative study of thermoelectric transport in the cuprates YBCO and La(1.8-x)Eu(0.2)Sr(x)CuO(4) (Eu-LSCO) to show that the two materials exhibit the same process of Fermi-surface reconstruction as a function of temperature and doping. The fact that in Eu-LSCO this reconstruction coexists with spin and charge modulations that break translational symmetry shows that stripe order is the generic non-superconducting ground state of hole-doped cuprates. PMID:21847106

  17. Global Phase Diagram of the High-Tc Cuprates

    NASA Astrophysics Data System (ADS)

    Chen, Han-Dong; Zhang, Shou-Cheng

    2006-02-01

    We propose a bosonic effective quantum Hamiltonian based on the projected SO(5) model with extended interactions, which can be derived from the microscopic models of the cuprates. The global phase diagram of this model is obtained using mean-field theory and the quantum Monte Carlo simulation. We show that this single quantum model can account for most salient features observed in the high-Tc cuprates, with different families of the cuprates attributed to different traces in the global phase diagram. A particular prediction of this theory is the checkerboard state of the d-wave hole pairs formed at certain magic filling fractions. We shall describe various properties of this state and present evidence that this novel state has been detected in recent STM and transport experiments.

  18. Crucial Role of Internal Collective Modes in Underdoped Cuprates

    NASA Astrophysics Data System (ADS)

    Mallik, Aabhaas V.; Yadav, Umesh K.; Medhi, Amal; Krishnamurthy, H. R.; Shenoy, Vijay B.

    The enigmatic cuprate superconductors have attracted resurgent interest with several recent reports and discussions of competing orders in the underdoped side. Motivated by this, here we address the natural question of frailty of the d-wave superconducting state in underdoped cuprates. Using a combination of theoretical approaches we study a t - J like model. We report an - as yet unexplored - instability that is brought about by an ``internal'' fluctuation (anti-symmetric mode) of the d-wave state. This new theoretical result helps in understanding recent ARPES and STM studies. We also suggest further experiments to uncover this physics. Work supported by CSIR, UGC, DST and DAE.

  19. Non-separable pairing interaction kernels applied to superconducting cuprates

    NASA Astrophysics Data System (ADS)

    Haley, Stephen B.; Fink, Herman J.

    2014-05-01

    A pairing Hamiltonian H(Γ) with a non-separable interaction kernel Γ produces HTS for relatively weak interactions. The doping and temperature dependence of Γ(x,T) and the chemical potential μ(x) is determined by a probabilistic filling of the electronic states in the cuprate unit cell. A diverse set of HTS and normal state properties is examined, including the SC phase transition boundary TC(x), SC gap Δ(x,T), entropy S(x,T), specific heat C(x,T), and spin susceptibility χs(x,T). Detailed x,T agreement with cuprate experiment is obtained for all properties.

  20. Exploring intertwined orders in cuprate superconductors

    DOE PAGESBeta

    Tranquada, John M.

    2014-11-22

    In this study, the concept of intertwined orders has been introduced to describe the cooperative relationship between antiferromagnetic spin correlations and electron (or hole) pair correlations that develop in copper-oxide superconductors. This contrasts with systems in which, for example, charge-density-wave (CDW) order competes for Fermi surface area with superconductivity. La2-xBaxCuO4 with x = 0.125 provides an example in which the ordering of spin stripes coincides with the onset of two-dimensional superconducting correlations. The apparent frustration of the interlayer Josephson coupling has motivated the concept of the pair-density-wave superconductor, a state that theoretical calculations show to be energetically competitive with themore » uniform d-wave superconductor. Even at x = 0.095, where there is robust superconductivity below 32 K in zero field, the coexistence of strong, low-energy, incommensurate spin excitations implies a spatially modulated and intertwined pair wave function. Recent observations of CDW order in YBa2Cu3O6+x and other cuprate families have raised interesting questions regarding the general role of charge modulations and the relation to superconductivity. While there are differences in the doping dependence of the modulation wave vectors in YBa2Cu3O6+x and La2-xBaxCuO4, the maximum ordering strength is peaked at the hole concentration of 1/8 in both cases. There are also possible connections with the quantum oscillations that have been detected about the same hole concentration but at high magnetic fields. Resolving these relationships remains a research challenge.« less

  1. Exploring intertwined orders in cuprate superconductors

    SciTech Connect

    Tranquada, John M.

    2014-11-22

    In this study, the concept of intertwined orders has been introduced to describe the cooperative relationship between antiferromagnetic spin correlations and electron (or hole) pair correlations that develop in copper-oxide superconductors. This contrasts with systems in which, for example, charge-density-wave (CDW) order competes for Fermi surface area with superconductivity. La2-xBaxCuO4 with x = 0.125 provides an example in which the ordering of spin stripes coincides with the onset of two-dimensional superconducting correlations. The apparent frustration of the interlayer Josephson coupling has motivated the concept of the pair-density-wave superconductor, a state that theoretical calculations show to be energetically competitive with the uniform d-wave superconductor. Even at x = 0.095, where there is robust superconductivity below 32 K in zero field, the coexistence of strong, low-energy, incommensurate spin excitations implies a spatially modulated and intertwined pair wave function. Recent observations of CDW order in YBa2Cu3O6+x and other cuprate families have raised interesting questions regarding the general role of charge modulations and the relation to superconductivity. While there are differences in the doping dependence of the modulation wave vectors in YBa2Cu3O6+x and La2-xBaxCuO4, the maximum ordering strength is peaked at the hole concentration of 1/8 in both cases. There are also possible connections with the quantum oscillations that have been detected about the same hole concentration but at high magnetic fields. Resolving these relationships remains a research challenge.

  2. Direct measurement of the upper critical field in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Grissonnanche, G.; Cyr-Choinière, O.; Laliberté, F.; René de Cotret, S.; Juneau-Fecteau, A.; Dufour-Beauséjour, S.; Delage, M.-È.; Leboeuf, D.; Chang, J.; Ramshaw, B. J.; Bonn, D. A.; Hardy, W. N.; Liang, R.; Adachi, S.; Hussey, N. E.; Vignolle, B.; Proust, C.; Sutherland, M.; Krämer, S.; Park, J.-H.; Graf, D.; Doiron-Leyraud, N.; Taillefer, Louis

    2014-02-01

    In the quest to increase the critical temperature Tc of cuprate superconductors, it is essential to identify the factors that limit the strength of superconductivity. The upper critical field Hc2 is a fundamental measure of that strength, yet there is no agreement on its magnitude and doping dependence in cuprate superconductors. Here we show that the thermal conductivity can be used to directly detect Hc2 in the cuprates YBa2Cu3Oy, YBa2Cu4O8 and Tl2Ba2CuO6+δ, allowing us to map out Hc2 across the doping phase diagram. It exhibits two peaks, each located at a critical point where the Fermi surface of YBa2Cu3Oy is known to undergo a transformation. Below the higher critical point, the condensation energy, obtained directly from Hc2, suffers a sudden 20-fold collapse. This reveals that phase competition—associated with Fermi-surface reconstruction and charge-density-wave order—is a key limiting factor in the superconductivity of cuprates.

  3. Direct measurement of the upper critical field in cuprate superconductors

    PubMed Central

    Grissonnanche, G.; Cyr-Choinière, O.; Laliberté, F.; René de Cotret, S.; Juneau-Fecteau, A.; Dufour-Beauséjour, S.; Delage, M. -È.; LeBoeuf, D.; Chang, J.; Ramshaw, B. J.; Bonn, D. A.; Hardy, W. N.; Liang, R.; Adachi, S.; Hussey, N. E.; Vignolle, B.; Proust, C.; Sutherland, M.; Krämer, S.; Park, J. -H.; Graf, D.; Doiron-Leyraud, N.; Taillefer, Louis

    2014-01-01

    In the quest to increase the critical temperature Tc of cuprate superconductors, it is essential to identify the factors that limit the strength of superconductivity. The upper critical field Hc2 is a fundamental measure of that strength, yet there is no agreement on its magnitude and doping dependence in cuprate superconductors. Here we show that the thermal conductivity can be used to directly detect Hc2 in the cuprates YBa2Cu3Oy, YBa2Cu4O8 and Tl2Ba2CuO6+δ, allowing us to map out Hc2 across the doping phase diagram. It exhibits two peaks, each located at a critical point where the Fermi surface of YBa2Cu3Oy is known to undergo a transformation. Below the higher critical point, the condensation energy, obtained directly from Hc2, suffers a sudden 20-fold collapse. This reveals that phase competition—associated with Fermi-surface reconstruction and charge-density-wave order—is a key limiting factor in the superconductivity of cuprates. PMID:24518054

  4. Ultrafast studies of coexisting electronic order in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Hinton, James; Thewalt, Eric; Alpichshev, Zhanybek; Sternbach, Aaron; McLeod, Alex; Ji, L.; Veit, Mike; Dorrow, Chelsey; Koralek, Jake; Xhao, Xudong; Barisic, Neven; Kemper, Alexander; Gedik, Nuh; Greven, Martin; Basov, Dimitri; Orenstein, Joe

    The cuprate family of high temperature superconductors displays a variety of electronic phases which emerge when charge carriers are added to the antiferromagnetic parent compound. These electronic phases are characterized by subtle differences in the low energy electronic excitations. Ultrafast time-resolved reflectivity (TRR) provides an ideal tool for investigating the cuprate phase diagram, as small changes in the electronic structure can produce significant contrast in the non-equilibrium reflectivity. Here we present TRR measurements of cuprate superconductors, focusing on the model single-layer cuprate HgBa2CuO4+δ. We observe a cusp-like feature in the quasiparticle lifetime near the superconducting transition temperature Tc. This feature can be understood using a model of coherently-mixed charge-density wave and superconducting pairing. We propose extending this technique to the nanoscale using ultrafast scattering scanning near-field microscopy (u-SNOM). This will allow us to explore how these electronic phases coexist and compete in real-space.

  5. Impedance and dielectric properties of mercury cuprate at nonsuperconducting state

    NASA Astrophysics Data System (ADS)

    Özdemir, Z. Güven; Çataltepe, Ö. Aslan; Onbaşlı, Ü.

    2015-10-01

    In this paper, impedance and dielectric properties of nonsuperconducting state of the mercury-based cuprate have been investigated by impedance measurements within the frequency interval of 10 Hz-10 MHz for the first time. The dielectric loss factor (tgδ) and ac conductivity (σac) parameters have also been calculated for non-superconducting state. According to impedance spectroscopy analysis, the equivalent circuit of the mercury cuprate system manifests itself as a semicircle in the Nyquist plot that corresponds to parallel connected resistance-capacitance circuit. The oscillation frequency of the circuit has been determined as approximately 45 kHz which coincides with the low frequency radio waves. Moreover, it has been revealed that the mercury-based cuprate investigated has high dielectric constants and hence it may be utilized in microelectronic industry such as capacitors, memory devices etc., at room temperature. In addition, negative capacitance (NC) effect has been observed for the mercury cuprate regardless of the operating temperatures at nonsuperconducting state. Referring to dispersions in dielectric properties, the main contribution to dielectric response of the system has been suggested as dipolar and interfacial polarization mechanisms.

  6. Insights on the Cuprate High Energy Anomaly Observed in ARPES

    SciTech Connect

    Moritz, Brian

    2011-08-16

    Recently, angle-resolved photoemission spectroscopy has been used to highlight an anomalously large band renormalization at high binding energies in cuprate superconductors: the high energy 'waterfall' or high energy anomaly (HEA). The anomaly is present for both hole- and electron-doped cuprates as well as the half-filled parent insulators with different energy scales arising on either side of the phase diagram. While photoemission matrix elements clearly play a role in changing the aesthetic appearance of the band dispersion, i.e. creating a 'waterfall'-like appearance, they provide an inadequate description for the physics that underlies the strong band renormalization giving rise to the HEA. Model calculations of the single-band Hubbard Hamiltonian showcase the role played by correlations in the formation of the HEA and uncover significant differences in the HEA energy scale for hole- and electron-doped cuprates. In addition, this approach properly captures the transfer of spectral weight accompanying doping in a correlated material and provides a unifying description of the HEA across both sides of the cuprate phase diagram. We find that the anomaly demarcates a transition, or cross-over, from a quasiparticle band at low binding energies near the Fermi level to valence bands at higher binding energy, assumed to be of strong oxygen character.

  7. Phase Separation in Cuprate Superconductors - Proceedings of the Workshop

    NASA Astrophysics Data System (ADS)

    Müller, K. A.; Benedek, G.

    1993-01-01

    The Table of Contents for the full book PDF is as follows: * Preface and Scope * Frustrated Phase Separation and High Temperature Superconductivity * Phase Separation and Photo-Induced High Tc Superconductivity in the Cuprates * Neutron Scattering Studies of the Spin Dynamics in La2-xSrxCuO4 * Percolative Phase Separation and High Tc Superconductivity * Phase Separation in Cuprate Superconductors from NMR and Microwave Absorption Measurements * Electronic Structure and Phase Separation in Superconducting Cuprates * The Virtual Exciton Mechanism of Superconductivity * Linear Arrays of Non Homogeneous Cu Sites in the CuO2 Plane: A New Scenario for Pairing Mechanisms in a Corrugated-Iron-Like Plane * Phase Separation, Structure and Superconductivity in Oxygen-Annealed La2CuO4+δ * Phase Separation in La2-xSrxCuO4 and YBa2Cu3Ox Studied by Mössbauer Spectroscopy * Phase Diagram and Transport Studies on La2-xSrxCuO4 * Static and Dynamic Transport Aspects of Phase Separation * Phase Separation in the Superconducting La2Cu4+δ Phases (0 < δ < 0.09) Prepared by Electrochemical Oxidation * Neutron Scattering Study of the YBa2Cu3O6+x System * NMR Investigation of Low Energy Excitations in YBa2Cu3O6+x Single Crystals * Aspects of the Spin Dynamics in the Cuprate Superconductors * Oxygen Order and Spin Structure in YBa2Cu3Ox Deduced from Copper NMR and NQR * Static and Dynamic Magnetic Properties of Ba, Cu and O in YBa2Cu4O8 and Y2Ba4Cu7O15.1 * Positional Splitting of Apex Oxygen and Nonlinear Excitations in Cuprates * Cooper Pair Formation by Distortive Electron-Lattice Coupling * Bipolaronic Charge Density Waves, Polaronic Spin Density Waves, and High Tc Superconductivity * Phase Separation as Result of a Thermodynamical Variational Method for the Emery Model * General Discussion led by G. Benedek and K. A. Müller

  8. Chiral plaquette polaron theory of cuprate superconductivity

    NASA Astrophysics Data System (ADS)

    Tahir-Kheli, Jamil; Goddard, William A., III

    2007-07-01

    Ab initio density functional calculations on explicitly doped La2-xSrxCuO4 find that doping creates localized holes in out-of-plane orbitals. A model for cuprate superconductivity is developed based on the assumption that doping leads to the formation of holes on a four-site Cu plaquette composed of the out-of-plane A1 orbitals apical Opz , planar Cud3z2-r2 , and planar Opσ . This is in contrast to the assumption of hole doping into planar Cudx2-y2 and Opσ orbitals as in the t-J model. Allowing these holes to interact with the d9 spin background leads to chiral polarons with either a clockwise or anticlockwise charge current. When the polaron plaquettes percolate through the crystal at x≈0.05 for La2-xSrxCuO4 , a Cudx2-y2 and planar Opσ band is formed. The computed percolation doping of x≈0.05 equals the observed transition to the “metallic” and superconducting phase for La2-xSrxCuO4 . Spin exchange Coulomb repulsion with chiral polarons leads to d -wave superconducting pairing. The equivalent of the Debye energy in phonon superconductivity is the maximum energy separation between a chiral polaron and its time-reversed partner. This energy separation is on the order of the antiferromagnetic spin coupling energy, Jdd˜0.1eV , suggesting a higher critical temperature. An additive skew-scattering contribution to the Hall effect is induced by chiral polarons and leads to a temperature dependent Hall effect that fits the measured values for La2-xSrxCuO4 . The integrated imaginary susceptibility, observed by neutron spin scattering, satisfies ω/T scaling due to chirality and spin-flip scattering of polarons along with a uniform distribution of polaron energy splittings. The derived functional form is compatible with experiments. The static spin structure factor for chiral spin coupling of the polarons to the undoped antiferromagnetic Cud9 spins is computed for classical spins on large two-dimensional lattices and is found to be incommensurate with a

  9. New avenues in the directed deprotometallation of aromatics: recent advances in directed cupration.

    PubMed

    Harford, Philip J; Peel, Andrew J; Chevallier, Floris; Takita, Ryo; Mongin, Florence; Uchiyama, Masanobu; Wheatley, Andrew E H

    2014-10-14

    Recent advances in the selective deprotometallation of aromatic reagents using alkali metal cuprates are reported. The ability of these synergic bases to effect deprotonation under the influence of a directing group is explored in the context of achieving new and more efficient organic transformations whilst encouraging greater ancillary group tolerance by the base. Developments in our understanding of the structural chemistry of alkali metal cuprates are reported, with both Gilman cuprates of the type R2CuLi and Lipshutz and related cuprates of the type R2Cu(X)Li2 (X = inorganic anion) elucidated and rationalised in terms of ligand sterics. The generation of new types of cuprate motif are introduced through the development of adducts between different classes of cuprate. The use of DFT methods to interrogate the mechanistic pathways towards deprotonative metallation is described. Theoretical modelling of in situ rearrangements undergone by the cuprate base are discussed, with a view to understanding the relationship between R2CuLi and R2Cu(X)Li2, their interconversion and the implications of this for cuprate reactivity. The advent of a new class of adduct between different cuprate types is developed and interpreted in terms of the options for expelling LiX from R2Cu(X)Li2. Applications in the field of medicinal chemistry and (hetero)arene derivatization are explored. PMID:24919957

  10. Enhanced Superconductivity in Superlattices of high-$T_c$ Cuprates

    SciTech Connect

    Okamoto, Satoshi; Maier, Thomas A

    2008-01-01

    The electronic properties of multilayers of strongly-correlated models for cuprate superconductors are investigated using cluster dynamical mean-field techniques. We focus on combinations of under-doped and over-doped layers and find that the superconducting order parameter in the over-doped layers is enhanced by the proximity effect of the strong pairing scale originating from the under-doped layers. The enhanced order parameter can even exceed the maximum value in uniform systems. This behavior is well reproduced in slave-boson mean-field calculations which also find higher transition temperatures than in the uniform system. These results indicate the possibility for higher critical temperatures in artificial cuprate multilayer systems.

  11. Puzzles about 1/8 magic doping in cuprate

    NASA Astrophysics Data System (ADS)

    Feng, D. L.; Shen, Z.-X.; Zhou, X. J.; Shen, K. M.; Lu, D. H.; Marel, D. V. D.

    2006-01-01

    We discuss the puzzles surrounding the interpretation of the 1/8 anomaly in cuprates, highlighting the tension between the real and reciprocal space ways to look at the problem. This issue is relevant to the current discussion on the nature of charge ordering in the form of ‘stripe’ and ‘checker-board’ as derived from neutron and STM experiments. A resolution of this tension is important to fully understand the electronic structure.

  12. Inhomogeneities in single crystals of cuprate oxide superconductors

    NASA Technical Reports Server (NTRS)

    Moorjani, K.; Bohandy, J.; Kim, B. F.; Adrian, F. J.

    1991-01-01

    The next stage in the evolution of experimental research on the high temperature superconductors will require high quality single crystals and epitaxially grown crystalline films. However, inhomogeneities and other defects are not uncommon in single crystals of cuprate oxide superconductors, so a corollary requirement will be a reliable method for judging the quality of these materials. The application of magnetically modulated resistance methods in this task is briefly described and illustrated.

  13. Experimental Evidence for Topological Doping in the Cuprates

    SciTech Connect

    Tranquada, J. M.

    1999-04-06

    Some recent experiments that provide support for the concept of topological doping in cuprate superconductors are discussed. Consistent with the idea of charge segregation, it is argued that the scattering associated with the ''resonance'' peak found in YBa{sub 2}Cu{sub 3}O{sub 6+x} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} comes from the Cu spins and not from the doped holes.

  14. Superconducting Clusters and Colossal Effects in Underdoped Cuprates

    NASA Astrophysics Data System (ADS)

    Alvarez, Gonzalo; Mayr, Matthias; Moreo, Adriana

    2005-03-01

    Phenomenological models for the antiferromagnetic vs. d-wave superconductivity competition in cuprates are studied[1] using conventional Monte Carlo techniques. The analysis suggests that cuprates may show a variety of different behaviors in the very underdoped regime: local coexistence, stripes, or, if disorder is present, states with nanoscale superconducting clusters. The transition from an antiferromagnetic to a superconducting state does not seem universal. In particular, inhomogeneous states lead to the possibility of colossal effects in some cuprates, analogous of those in manganites. Under suitable conditions, non-superconducting Cu-oxides could rapidly[2] become superconducting by the influence of weak perturbations that align the randomly oriented phases of the superconducting clusters in the mixed state. Consequences of these ideas for angle resolved photoemission and scanning tunneling microscopy experiments[3] will also discussed. [1] Alvarez et al., cond-mat/0401474, to appear in PRB. [2] I. Bozovic et al., PRL 93, 157002, (2004) [3] A. Ino et al., PRB 62, 4127 (2000); K. Lang et al, Nature 415, 412 (2002). Research performed in part at the Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract DE-AC05-00OR22725.

  15. Doping dependence of Meissner effect in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Feng, Shiping; Huang, Zheyu; Zhao, Huaisong

    2010-11-01

    Within the t- t‧- J model, the doping dependence of the Meissner effect in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. Following the linear response theory, it is shown that the electromagnetic response consists of two parts, the diamagnetic current and the paramagnetic current, which exactly cancels the diamagnetic term in the normal state, and then the Meissner effect is obtained for all the temperature T ⩽ Tc throughout the superconducting dome. By considering the two-dimensional geometry of cuprate superconductors within the specular reflection model, the main features of the doping and temperature dependence of the local magnetic field profile, the magnetic field penetration depth, and the superfluid density observed on cuprate superconductors are well reproduced. In particular, it is shown that in analogy to the domelike shape of the doping dependent superconducting transition temperature, the maximal superfluid density occurs around the critical doping δ ≈ 0.195, and then decreases in both lower doped and higher doped regimes.

  16. Atomic-Layer Engineering of Cuprate Superconductors (415th Brookhaven Lecture)

    SciTech Connect

    Bozovic, Ivan

    2006-05-17

    Copper-oxide compounds, called cuprates, show superconducting properties at 163 degrees Kelvin, the highest temperature of any known superconducting material. Cuprates are therefore among the 'high-temperature superconductors' of extreme interest both to scientists and to industry. Research to learn their secrets is one of the hottest topics in the field of materials science.

  17. Sr2IrO4: Gateway to cuprate superconductivity?

    SciTech Connect

    Mitchell, J. F.

    2015-06-05

    High temperature superconductivity in cuprates remains a defining challenge in condensed matter physics. Recently, a new set of related compounds based on Ir rather than Cu has been discovered that may be on the verge of superconductivity themselves or be able to shed new light on the underlying interactions responsible for superconductivity in the cuprates.

  18. 40 CFR 721.10488 - Cuprate, [[[[[[[ (sulfonaphthalenyl)]azo]-(substitutedphenyl)]azo]-(substitutedsulfonaphthalenyl...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cuprate, azo]-(substitutedphenyl)]azo]-(substitutedsulfonaphthalenyl)] azo] - substituted phenyl - substituted heteromonocycle], sodium salts (generic). 721.10488... Substances § 721.10488 Cuprate, azo]-(substitutedphenyl)]azo]-(substitutedsulfonaphthalenyl)]...

  19. 40 CFR 721.10488 - Cuprate, [[[[[[[ (sulfonaphthalenyl)]azo]- (substitutedphenyl)]azo...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cuprate, azo]- (substitutedphenyl)]azo]- (substitutedsulfonaphthalenyl)] azo]- substituted phenyl- substituted heteromonocycle], sodium salts (generic). 721.10488... Substances § 721.10488 Cuprate, azo]- (substitutedphenyl)]azo]- (substitutedsulfonaphthalenyl)]...

  20. Hidden Fermionic Excitation Boosting High-Temperature Superconductivity in Cuprates

    NASA Astrophysics Data System (ADS)

    Sakai, Shiro; Civelli, Marcello; Imada, Masatoshi

    2016-02-01

    The dynamics of a microscopic cuprate model, namely, the two-dimensional Hubbard model, is studied with a cluster extension of the dynamical mean-field theory. We find a nontrivial structure of the frequency-dependent self-energies, which describes an unprecedented interplay between the pseudogap and superconductivity. We show that these properties are well described by quasiparticles hybridizing with (hidden) fermionic excitations, emergent from the strong electronic correlations. The hidden fermion enhances superconductivity via a mechanism distinct from a conventional boson-mediated pairing, and originates the normal-state pseudogap. Though the hidden fermion is elusive in experiments, it can solve many experimental puzzles.

  1. Angle-resolved photoemission spectroscopy (ARPES) studies of cuprate superconductors

    SciTech Connect

    Palczewski, Ari Deibert

    2010-01-01

    This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl2Ba2CuO6+δ (Tl2201) Tc, max ≈ 95 K and (Bi 1.35Pb0.85)(Sr1.47La0.38)CuO6+δ (Bi2201) Tc, max ≈ 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major differences in the band structure. First, the Fermi surface segments close to (π,0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher Tc Tl2201. The second study looks at the different ways of doping Bi2Sr2CaCu2O8+δ (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the absorption of oxygen from CO2/CO molecules, prime contaminants present in UHV systems. Second, in a very clean UHV system at elevated temperatures (above about 200 K), the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. The final study probed the particle-hole symmetry of the pseudogap phase in high temperature superconducting cuprates by looking at the thermally excited bands above the Fermi level. The data showed a particle-hole symmetric pseudogap which symmetrically closes away from the nested FS before the node. The data is consistent

  2. Thermomagnetic effects above and below {Tc} in the cuprate superconductors

    SciTech Connect

    Clayhold, J.A.; Xue, Y.Y.; Chu, C.W.; Eckstein, J.N.; Bozovic, I.

    1996-12-31

    Two different thermomagnetic transport quantities, the electrothermal conductivity and the Nernst effect are shown to be powerful probes of high-temperature superconductors. In the vortex state below {Tc}, the electrothermal conductivity is independent of both the magnetic field and the vortex viscosity because it is sensitive only to the properties of the vortex normal cores. Some new data from cuprate superconductors show a surprising, low-field anomaly in the dilute vortex limit. Above {Tc} in the normal state, it is shown how the Nernst effect is a probe of transport anisotropy around the Fermi surface.

  3. Atomic layer-by-layer epitaxy of cuprate superconductors

    SciTech Connect

    Bozovic, I.; Eckstein, J.N.; Virshup, G.F.

    1994-03-01

    A technique for atomic layer-by-layer epitaxy of cuprate superconductors and other complex oxides has been developed at Varian. The samples are engineered by stacking molecular layers of different compounds to assemble multilayers and superlattices, by adding or omitting atomic monolayers to create novel compounds, and by doping within specified atomic monolayers. Apart form manufacturing trilayer Josephson junctions with I{sub c}R{sub n}>5 mV, this technique enables one to address fundamental issues such as the dimensionality of HTSC state, existence of long-range proximity effects, occurrence of resonant tunneling etc., as well as to synthesize novel metastable HTSC compounds. 4 refs., 2 figs.

  4. Cold-spots and glassy nematicity in underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Lee, Kyungmin; Kivelson, Steven A.; Kim, Eun-Ah

    2016-07-01

    There is now copious direct experimental evidence of various forms of (short-range) charge order in underdoped cuprate high temperature superconductors, and spectroscopic signatures of a nodal-antinodal dichotomy in the structure of the single-particle spectral functions. In this context we analyze the Bogoliubov quasiparticle spectrum in a superconducting nematic glass. The coincidence of the superconducting "nodal points" and the nematic "cold-spots" on the Fermi surface naturally accounts for many of the most salient features of the measured spectral functions (from angle-resolved photoemission) and the local density of states (from scanning tunneling microscopy).

  5. Hidden Fermionic Excitation Boosting High-Temperature Superconductivity in Cuprates.

    PubMed

    Sakai, Shiro; Civelli, Marcello; Imada, Masatoshi

    2016-02-01

    The dynamics of a microscopic cuprate model, namely, the two-dimensional Hubbard model, is studied with a cluster extension of the dynamical mean-field theory. We find a nontrivial structure of the frequency-dependent self-energies, which describes an unprecedented interplay between the pseudogap and superconductivity. We show that these properties are well described by quasiparticles hybridizing with (hidden) fermionic excitations, emergent from the strong electronic correlations. The hidden fermion enhances superconductivity via a mechanism distinct from a conventional boson-mediated pairing, and originates the normal-state pseudogap. Though the hidden fermion is elusive in experiments, it can solve many experimental puzzles. PMID:26894730

  6. Quasiparticles in the pseudogap Phase of Underdoped Cuprate

    SciTech Connect

    Yang, K.; Yang, H; Johnson, P; Rice, T; Zhang, F

    2009-01-01

    Recent angle-resolved photoemission (Yang H.-B. et al., Nature, 456 (2008) 77) and scanning tunneling microscopy (Kohsaka Y. et al., Nature, 454 (2008) 1072) measurements on underdoped cuprates have yielded new spectroscopic information on quasiparticles in the pseudogap phase. New features of the normal state such as particle-hole asymmetry, maxima in the energy dispersion, and accompanying drops in the spectral weight of quasiparticles agree with the ansatz of Yang et al. for the single-particle propagator in the pseudogap phase. The coherent quasiparticle dispersion and reduced asymmetry in the tunneling density of states in the superconducting state can also be described by this propagator.

  7. Direct Hydroxylation and Amination of Arenes via Deprotonative Cupration.

    PubMed

    Tezuka, Noriyuki; Shimojo, Kohei; Hirano, Keiichi; Komagawa, Shinsuke; Yoshida, Kengo; Wang, Chao; Miyamoto, Kazunori; Saito, Tatsuo; Takita, Ryo; Uchiyama, Masanobu

    2016-07-27

    Deprotonative directed ortho cupration of aromatic/heteroaromatic C-H bond and subsequent oxidation with t-BuOOH furnished functionalized phenols in high yields with high regio- and chemoselectivity. DFT calculations revealed that this hydroxylation reaction proceeds via a copper (I → III → I) redox mechanism. Application of this reaction to aromatic C-H amination using BnONH2 efficiently afforded the corresponding primary anilines. These reactions show broad scope and good functional group compatibility. Catalytic versions of these transformations are also demonstrated. PMID:27348154

  8. Ong construction for the reconstructed Fermi surface of underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Robinson, P.; Hussey, N. E.

    2015-12-01

    Using the Ong construction for a two-dimensional metal, we show that the sign change in the Hall coefficient RH of underdoped hole-doped cuprates at low temperature is consistent with the emergence of biaxial charge order recently proposed to explain the observation of low-frequency quantum oscillations. The sharp evolution of RH with temperature, however, can only be reconciled by incorporating a highly anisotropic quasiparticle scattering rate. The magnitude and form of the scattering rate extracted from the fitting imply that those quasiparticles at the vertices of the reconstructed pocket(s) approach the boundary of incoherence at the onset of charge order.

  9. Fluctuating charge-density waves in a cuprate superconductor.

    PubMed

    Torchinsky, Darius H; Mahmood, Fahad; Bollinger, Anthony T; Božović, Ivan; Gedik, Nuh

    2013-05-01

    Cuprate materials hosting high-temperature superconductivity (HTS) also exhibit various forms of charge and spin ordering whose significance is not fully understood. So far, static charge-density waves (CDWs) have been detected by diffraction probes only at particular doping levels or in an applied external field . However, dynamic CDWs may also be present more broadly and their detection, characterization and relationship with HTS remain open problems. Here we present a method based on ultrafast spectroscopy to detect the presence and measure the lifetimes of CDW fluctuations in cuprates. In an underdoped La(1.9)Sr(0.1)CuO4 film (T(c) = 26 K), we observe collective excitations of CDW that persist up to 100 K. This dynamic CDW fluctuates with a characteristic lifetime of 2 ps at T = 5 K that decreases to 0.5 ps at T = 100 K. In contrast, in an optimally doped La(1.84)Sr(0.16)CuO4 film (T(c) = 38.5 K), we detect no signatures of fluctuating CDWs at any temperature, favouring the competition scenario. This work forges a path for studying fluctuating order parameters in various superconductors and other materials. PMID:23435216

  10. Hybrid crystals of cuprates and iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Xia, Dai; Cong-Cong, Le; Xian-Xin, Wu; Jiang-Ping, Hu

    2016-07-01

    We propose two possible new compounds, Ba2CuO2Fe2As2 and K2CuO2Fe2Se2, which hybridize the building blocks of two high temperature superconductors, cuprates and iron-based superconductors. These compounds consist of square CuO2 layers and antifluorite-type Fe2 X 2 (X = As, Se) layers separated by Ba/K. The calculations of binding energies and phonon spectra indicate that they are dynamically stable, which ensures that they may be experimentally synthesized. The Fermi surfaces and electronic structures of the two compounds inherit the characteristics of both cuprates and iron-based superconductors. These compounds can be superconductors with intriguing physical properties to help to determine the pairing mechanisms of high T c superconductivity. Project supported by the National Basic Research Program of China (Grant No. 2015CB921300), the National Natural Science Foundation of China (Grant Nos. 1190020 and 11334012), and the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB07000000).

  11. Luttinger Liquid, Singular Interaction and Quantum Criticality in Cuprate Materials

    NASA Astrophysics Data System (ADS)

    di Castro, C.; Caprara, S.

    2014-10-01

    With particular reference to the role of the renormalization group (RG) approach and Ward identities (WI's), we start by recalling some old features of the one-dimensional Luttinger liquid as the prototype of non-Fermi-liquid behavior. Its dimensional crossover to the Landau normal Fermi liquid implies that a non-Fermi liquid, as, e.g., the normal phase of the cuprate high temperature superconductors, can be maintained in d > 1 only in the presence of a sufficiently singular effective interaction among the charge carriers. This is the case when, nearby an instability, the interaction is mediated by critical fluctuations. We are then led to introduce the specific case of superconductivity in cuprates as an example of avoided quantum criticality. We will disentangle the fluctuations which act as mediators of singular electron-electron interaction, enlightening the possible order competing with superconductivity and a mechanism for the non-Fermi-liquid behavior of the metallic phase. This paper is not meant to be a comprehensive review. Many important contributions will not be considered. We will also avoid using extensive technicalities and making full calculations for which we refer to the original papers and to the many good available reviews. We will here only follow one line of reasoning which guided our research activity in this field.

  12. Paired electron pockets in the hole-doped cuprates

    NASA Astrophysics Data System (ADS)

    Galitski, Victor; Sachdev, Subir

    2009-04-01

    We propose a theory for the underdoped hole-doped cuprates, focusing on the “nodal-antinodal dichotomy” observed in recent experiments. Our theory begins with an ordered antiferromagnetic Fermi liquid with electron and hole pockets. We argue that it is useful to consider a quantum transition at which the loss of antiferromagnetic order leads to a hypothetical metallic “algebraic charge liquid” (ACL) with pockets of charge -e and +e fermions, and an emergent U(1) gauge field; the instabilities of the ACL lead to the low-temperature phases of the underdoped cuprates. The pairing instability leads to a superconductor with the strongest pairing within the -e Fermi pockets, a d -wave pairing signature for electrons, and very weak nodal-point pairing of the +e fermions near the Brillouin-zone diagonals. The influence of an applied magnetic field is discussed using a proposed phase diagram as a function of field strength and doping. We describe the influence of gauge field and pairing fluctuations on the quantum Shubnikov-de Haas oscillations in the normal states induced by the field. For the finite-temperature pseudogap region, our theory has some similarities to the phenomenological two-fluid model of -2e bosons and +e fermions proposed by Geshkenbein [Phys. Rev. B 55, 3173 (1997)], which describes anomalous aspects of transverse transport in a magnetic field.

  13. Searching for spectroscopic signatures of density wave correlations in cuprates

    NASA Astrophysics Data System (ADS)

    He, Rui-Hua

    2015-03-01

    Recent developments in the research on high-temperature cuprate superconductors highlight the relevance of some density wave correlations to the superconductivity and its normal state in this generic class of materials. Depending on specific cuprate systems, these density wave correlations can have diverse manifestations in different (charge, spin, pairing) sectors and likely break (time reversal, space inversion, point group, gauge) symmetries in addition to the lattice translation. A unified understanding of their microscopic nature hinges on further characterizations using direct (imaging scattering) probes for these correlations themselves, as well as indirect probes for their interplay with other degrees of freedom in the system. ARPES can provide information about a density wave order through probing modifications in the electron structure it induces, while other spectroscopy techniques can shed unique lights on the broken symmetry aspect of the order. In this talk, I will review the density-wave signatures that have been or yet to be found in ARPES mainly in terms of the spectral weight, energy gap, and renormalized band dispersions. These experimental observations/proposals, coupled with simple theoretical modeling, promise new insights into the (wavevector, order parameter, form factor) characters of associated density wave correlations. Time permitting, I will introduce a novel x-ray spectroscopy technique that can detect broken time-reversal versus space-inversion symmetry of an electronic order in a way complementary to the polar Kerr effect.

  14. Lorenz number in cuprates: digital evidence for bipolarons

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sasha

    2003-03-01

    Strong electron-phonon interaction in the cuprates has gathered support over the last decade in a number of experiments. While phonons remain almost unrenormalised, electrons are transformed into itinerant bipolarons and thermally excited polarons when the electron-phonon interaction is strong. We calculate the Lorenz number of the system to show that the Wiedemann-Franz law breaks down because of the interference of polaron and bipolaron contributions in the heat flow [1]. The model fits numerically the experimental Hall Lorenz number [2], which provides a digital evidence for bipolarons in the cuprates. *Mailing address: Department of Physics, Loughborough University, Loughborough LE11 3TU, United Kingdom; E-mail: a.s.alexandrov@lboro.ac.uk; Phone: (44) 1509 223303; Fax: (44) 1509 223986. [1] K. K. Lee, W. Y. Liang, A. S. Alexandrov (2002) unpublished. [2] Y. Zhang, N.P. Ong, Z.A. Xu, K. Krishana, R. Gagnon, and L.Taillefer, Phys. Rev. Lett., 84, 2219 (2000).

  15. Anticorrelation between the parent charge transfer gap and maximum transition temperature in cuprates

    NASA Astrophysics Data System (ADS)

    Ruan, Wei; Hu, Cheng; Cai, Peng; Peng, Yingying; Li, Xintong; Hao, Zhenqi; Zhou, Xingjiang; Weng, Zheng-Yu; Wang, Yayu

    We use scanning tunneling spectroscopy to measure the electronic structure of the parent Mott insulator of three different types of cuprates. The charge transfer gap size exhibits pronounced variations, and more interestingly it shows an anticorrelation with the maximum superconducting transition temperature achieved at the optimal doping of each cuprate. This result suggests that the Mottness in parent cuprate plays a crucial role in determining the superconducting properties. In particular, reducing the electron correlation strength enhances superconductivity, which is consistent with the pairing mechanism based on the doped Mott insulator picture.

  16. μSR Studies on Magnetism in High-Tc Cuprates

    NASA Astrophysics Data System (ADS)

    Koike, Yoji; Adachi, Tadashi

    2016-09-01

    Since the discovery of high-Tc superconductivity in cuprates, muon spin relaxation (μSR) measurements have greatly contributed to the understanding of high-Tc superconductivity. In this paper, μSR studies on the magnetism in high-Tc cuprates obtained these past three decades are reviewed. Antiferromagnetic long-range order, 1/8 anomaly, stripes of Cu spins and holes, impurity-induced magnetism, magnetic-field-induced magnetism, pseudogap, ferromagnetism in the heavily overdoped regime, and undoped superconductivity in T'-type cuprates are discussed. Moreover, the fundamentals of μSR measurements for the study of magnetism are described for μSR beginners.

  17. Role of Pressure and Magnetic Scattering on the Tc of the Cuprates

    NASA Astrophysics Data System (ADS)

    Wolf, Stuart; Kresin, Vladimir; Ovchinnikov, Yurii

    1996-03-01

    We can show that the large pressure effects on the transition temperature in the superconducting cuprates are caused by an unusual interplay between carrier doping and pair-breaking scattering. This pair-breaking scattering leads to a depression of Tc relative to its intrinsic value which we find to be in the range of 160K. Using these ideas we can explain the relative transition temperature in the one, two, and three layer cuprates as well as estimate the maximum Tc for the cuprate family of superconductors.

  18. The microscopic structure of charge order in cuprates

    NASA Astrophysics Data System (ADS)

    Comin, Riccardo

    2015-03-01

    The spontaneous self-arrangement of electrons into periodically modulated patterns, a phenomenon commonly termed as charge order or charge-density-wave (CDW), has recently resurfaced as a prominent, universal ingredient for the physics of high-temperature superconductors. In such context, resonant x-ray scattering (RXS) has rapidly become the technique of choice for the study of charge order in momentum space, owing to its ability to directly identify a breaking of translational symmetry in the electronic density. In this talk, I will present our recent RXS studies of charge order in Bi2201, which reconciled years of apparently disconnected findings in different cuprate families by showing how charge order is a universal phenomenon in hole-doped cuprates [R. Comin, et al., Charge Order Driven by Fermi-Arc Instability in Bi2Sr2 - xLaxCuO6 +d, Science 343, 390 (2014)]. Contextually, I will discuss very recent findings of charge order in NCCO, which project such phenomenology to the electron-doped materials [E. da Silva Neto*, R. Comin*, et al., Charge ordering in the electron-doped superconductor Nd2-xCexCuO4, accepted (2014) - preprint at: http://arxiv.org/abs/1410.2253]. Furthermore, in YBCO, we have succeeded to fully reconstruct the CDW order parameter in the two-dimensional momentum space and demonstrate how resonant x-ray methods can be used to peer into the microscopic structure and symmetry of the charge order. Using this new method, we have been able to demonstrate the presence of charge stripes at the nanoscale [R. Comin, et al., Broken translational and rotational symmetry via charge stripe order in underdoped YBa2Cu3O6 +y, under review (2014)], as well as evaluate the local symmetry in the charge distribution around the Cu atoms, which was found to be predominantly of a d-wave bond-order type [R. Comin, et al., The symmetry of charge order in cuprates, under review (2014) - preprint at: http://arxiv.org/abs/1402.5415].

  19. Elastic moduli across the superconducting and pseudogap phase boundaries in four cuprate compounds

    NASA Astrophysics Data System (ADS)

    Ramshaw, Brad; Shekhter, Arkady; Betts, Jon; Migliori, Albert

    2013-03-01

    A detailed understanding of the physics of the cuprate superconductors relies on an experimental determination of the thermodynamic phase diagram. Resonant ultrasound spectroscopy (RUS) is a unique thermodynamic probe, capable of measuring part per million changes in elastic moduli, and has access to symmetry information. Here we present a symmetry analysis of changes in the elastic moduli across the superconducting and psedogap phase boundaries in several classes of cuprates: YBCO, LSCO, Hg-1201, and Tl-2201.

  20. Theoretical study of magnetoelectric effects in noncentrosymmetric and cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Kashyap, Manoj K.

    A century after the discovery of superconductivity at the lab of Kamerlingh Onnes in 1911, it is noticeable that the phenomenon is quite ubiquitous in nature. In addition to a long list of superconducting alloys and compounds, almost half the elements in the periodic table superconduct. By the late seventies, superconductivity was thought to be well understood. This turned out to be a myth, with the discovery of unconventional superconductors that defied Bardeen-Cooper-Schrieffer (BCS) theory. Cuprates have been the most prominent example among them ever since their discovery in 1986 by Bednorz and Muller. Another example of non-compliance with BCS theory lie among noncentrosymmetric superconductors. In this dissertation, magnetoelectric (ME) effects in these two classes of superconductors have been studied from different perspectives, utilizing Ginzburg-Landau (GL) theory. Even though GL theory was proposed before the BCS theory, it was not given much importance due to its phenomenological nature until Gor'kov proved that it is a limiting form of the microscopic BCS theory. However today, in the absence of any complete microscopic theory to explain superconductivity in unconventional superconductors, Ginzburg-Landau theory is an important tool to move ahead and qualitatively understand the behavior of varied superconducting systems. Noncentrosymmetric superconductors have generated much theoretical interest since 2004 despite been known for long. The absence of inversion symmetry in non- centrosymmetric superconductors allows for extra terms called Lifshitz invariants in the Ginzburg-Landau functional. This leads to magnetoelectric effects that do not exist in centrosymmetric superconductors. One manifestation of this is in the vortex structure in materials with a cubic point group O. In particular, a current is predicted to flow parallel to the applied magnetic field in such a vortex in addition to the usual vortex supercurrents. In this work, we present both

  1. Nonequilibrium phase transitions in cuprates observed by ultrafast electron crystallography.

    PubMed

    Gedik, Nuh; Yang, Ding-Shyue; Logvenov, Gennady; Bozovic, Ivan; Zewail, Ahmed H

    2007-04-20

    Nonequilibrium phase transitions, which are defined by the formation of macroscopic transient domains, are optically dark and cannot be observed through conventional temperature- or pressure-change studies. We have directly determined the structural dynamics of such a nonequilibrium phase transition in a cuprate superconductor. Ultrafast electron crystallography with the use of a tilted optical geometry technique afforded the necessary atomic-scale spatial and temporal resolutions. The observed transient behavior displays a notable "structural isosbestic" point and a threshold effect for the dependence of c-axis expansion (Deltac) on fluence (F), with Deltac/F = 0.02 angstrom/(millijoule per square centimeter). This threshold for photon doping occurs at approximately 0.12 photons per copper site, which is unexpectedly close to the density (per site) of chemically doped carriers needed to induce superconductivity. PMID:17446397

  2. Antiferromagnetic superconducting state in the electron-doped cuprates?

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Markiewicz, Robert S.; Bansil, Arun

    2006-03-01

    Recent angle-resolved photoemission (ARPES) studies of the electron-doped cuprate Nd2-xCexCuO4 (NCCO)[1] have been interpreted in terms of a uniform antiferromagnetic (AF) metal, with doping into the upper magnetic band and gap collapse close to optimal doping[2]. An open question is whether the system remains uniform in the simultaneous presence of AF and (d- wave) superconducting (SC) order. Here, we explore the properties of a uniform AF-SC model for NCCO, to ascertain to what extent we can explain anomalous features, such as the nonmonotonic angle dependence of the superconducting gap[3]. Work supported by the USDOE. [1] N.P. Armitage, et al., PRL 87, 147003 (2002). [2] C. Kusko, et al., PRB66, 140513 (2002); A.-M.S. Tremblay, et al., cond-mat/0511334. [3] H. Matsui, et al., PRL 95, 017003 (2005).

  3. Optical studies of high-temperature superconducting cuprates.

    PubMed

    Tajima, Setsuko

    2016-09-01

    The optical studies of high-temperature superconducting cuprates (HTSC) are reviewed. From the doping dependence of room temperature spectra, a dramatic change of the electronic state from a Mott (charge transfer) insulator to a Fermi liquid has been revealed. Additionally, the unusual 2D nature of the electronic state has been found. The temperature dependence of the optical spectra provided a rich source of information on the pseudogap, superconducting gap, Josephson plasmon, transverse Josephson plasma mode and precursory superconductivity. Among these issues, Josephson plasmons and transverse Josephson plasma mode were experimentally discovered by optical measurements, and thus are unique to HTSC. The effect of the spin/charge stripe order is also unique to HTSC, reflecting the conducting nature of the stripe order in this system. The pair-breaking due to the stripe order seems stronger in the out-of-plane direction than in the in-plane one. PMID:27472654

  4. Charge orders, magnetism and pairings in the cuprate superconductors.

    PubMed

    Kloss, T; Montiel, X; de Carvalho, V S; Freire, H; Pépin, C

    2016-08-01

    We review the recent developments in the field of cuprate superconductors with special focus on the recently observed charge order in the underdoped compounds. We introduce new theoretical developments following the study of the antiferromagnetic quantum critical point in two dimensions, in which preemptive orders in both charge and superconducting (SC) sectors emerge, that are in turn related by an SU(2) symmetry. We consider the implications of this proliferation of orders in the underdoped region, and provide a study of the type of fluctuations which characterize the SU(2) symmetry. We identify an intermediate energy scale where the SC fluctuations are dominant and argue that they are unstable towards the formation of a resonant excitonic state at the pseudogap temperature T (*). We discuss the implications of this scenario for a few key experiments. PMID:27427401

  5. Strong-coupling approach to nematicity in the cuprates

    NASA Astrophysics Data System (ADS)

    Orth, Peter Philipp; Jeevanesan, Bhilahari; Schmalian, Joerg; Fernandes, Rafael

    The underdoped cuprate superconductor YBa2Cu3O7-δ is known to exhibit an electronic nematic phase in proximity to antiferromagnetism. While nematicity sets in at large temperatures of T ~ 150 K, static spin density wave order only emerges at much lower temperatures. The magnetic response shows a strong in-plane anisotropy, displaying incommensurate Bragg peaks along one of the crystalline directions and a commensurate peak along the other one. Such an anisotropy persists even in the absence of long-range magnetic order at higher temperatures, marking the onset of nematic order. Here we theoretically investigate this situation using a strong-coupling method that takes into account both the localized Cu spins and the holes doped into the oxygen orbitals. We derive an effective spin Hamiltonian and show that charge fluctuations promote an enhancement of the nematic susceptibility near the antiferromagnetic transition temperature.

  6. Complete symmetry analysis of the Raman spectra in cuprates

    NASA Astrophysics Data System (ADS)

    Venturini, F.; Zhang, Q.-M.; Hackl, R.; Erb, A.; Berger, H.; Revaz, B.; Nagao, Y.; Ando, Y.

    2002-03-01

    We describe results of Raman scattering measurements on differently doped cuprate single crystals. We performed a complete polarization analysis, using circular in addition to the commonly used linear polarizations. This allowed us to determine all symmetry components of the Raman signal being characteristic for tetragonal systems, including A_2g excitations which indicate the presence of a time-reversal broken symmetry in these systems. The A_2g signal has an intensity comparable to that of the other symmetries, but exhibits a distinctly different frequency dependence. In particular, there is a gap at low energies which decreases with increasing doping. The Raman relaxation rates and mass renormalization factor extracted from the pure B_1g and B_2g spectra are consistent with IR-results, and the unphysical drop of 1+λ(ω) below unity for high frequencies disappears teopel. 99 opel M. Opel et al., Phys. Rev. B 61, 9752 (2000). thebibliography

  7. Effect of Extended Saddle Point Singularities in Cuprates and Evidences

    NASA Astrophysics Data System (ADS)

    Zhao, Guang-Lin

    First-principles calculations and angle-resolved photoemission spectroscopy measurements showed extended saddle point singularities in the electron structures of some cuprates such as YBa2Cu3O7 (YBCO). The extended saddle point singularities in the electronic structures of the materials can lead to anomalous physical properties. In this work, a new methodology is implemented by integrating first-principles calculations of electronic structures of the materials into the theory of many-body physics for superconductivity. The aim is to seek a unified methodology to calculate the electronic and superconducting properties of the materials. It is demonstrated from first-principles that the extended saddle point singularities in the materials such as YBCO strongly correlate to the anomalous isotope effect in the superconductors. The work was funded in part by NSF LASIGMA Project (Award # EPS-1003897, NSF92010-15-RII-SUBR) and by ARO (Award # W911NF-15-1-0483).

  8. Spin excitations of ferronematic order in underdoped cuprate superconductors

    PubMed Central

    Seibold, G.; Di Castro, C.; Grilli, M.; Lorenzana, J.

    2014-01-01

    High-temperature superconductors exhibit a characteristic hourglass-shaped spectrum of magnetic fluctuations which most likely contribute to the pairing glue in the cuprates. Recent neutron scattering experiments in strongly underdoped compounds have revealed a significant low energy anisotropy of these fluctuations which we explain by a model in which topological defects of the antiferromagnet clump to producing domain wall segments with ferronematic order. This state does not invoke global charge order but breaks C4 rotational and inversion symmetry. The incommensurability of the low doping charge-disordered state is in good agreement with experiment and interpolates smoothly with the incommensurability of the stripe phase at higher doping. Within linear spin-wave theory the dynamic structure factor is in very good agreement with inelastic neutron scattering data and can account for the observed energy dependent anisotropy. PMID:24936723

  9. Optical studies of high-temperature superconducting cuprates

    NASA Astrophysics Data System (ADS)

    Tajima, Setsuko

    2016-09-01

    The optical studies of high-temperature superconducting cuprates (HTSC) are reviewed. From the doping dependence of room temperature spectra, a dramatic change of the electronic state from a Mott (charge transfer) insulator to a Fermi liquid has been revealed. Additionally, the unusual 2D nature of the electronic state has been found. The temperature dependence of the optical spectra provided a rich source of information on the pseudogap, superconducting gap, Josephson plasmon, transverse Josephson plasma mode and precursory superconductivity. Among these issues, Josephson plasmons and transverse Josephson plasma mode were experimentally discovered by optical measurements, and thus are unique to HTSC. The effect of the spin/charge stripe order is also unique to HTSC, reflecting the conducting nature of the stripe order in this system. The pair-breaking due to the stripe order seems stronger in the out-of-plane direction than in the in-plane one.

  10. Charge orders, magnetism and pairings in the cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Kloss, T.; Montiel, X.; de Carvalho, V. S.; Freire, H.; Pépin, C.

    2016-08-01

    We review the recent developments in the field of cuprate superconductors with special focus on the recently observed charge order in the underdoped compounds. We introduce new theoretical developments following the study of the antiferromagnetic quantum critical point in two dimensions, in which preemptive orders in both charge and superconducting (SC) sectors emerge, that are in turn related by an SU(2) symmetry. We consider the implications of this proliferation of orders in the underdoped region, and provide a study of the type of fluctuations which characterize the SU(2) symmetry. We identify an intermediate energy scale where the SC fluctuations are dominant and argue that they are unstable towards the formation of a resonant excitonic state at the pseudogap temperature T *. We discuss the implications of this scenario for a few key experiments.

  11. A “midinfrared” scenario for cuprate superconductivity

    PubMed Central

    Leggett, A. J.

    1999-01-01

    I conjecture that the mechanism of superconductivity in the cuprates is a saving, due to the improved screening resulting from Cooper pair formation, of the part of the Coulomb energy associated with long wavelengths and midinfrared frequencies. This scenario is shown to provide a plausible explanation of the trend of transition temperature with layering structure in the Ca-spaced compounds and to predict a spectacularly large decrease in the electron-energy-loss spectroscopy cross-section in the midinfrared region on transition to the superconducting state, as well as less spectacular but still surprisingly large changes in the optical behavior. Existing experimental results appear to be consistent with this picture. PMID:10411881

  12. Unconventional proximity effect and inverse spin-switch behavior in a model manganite-cuprate-manganite trilayer system

    SciTech Connect

    Salafranca Laforga, Juan I; Okamoto, Satoshi

    2010-01-01

    The proximity effect in a model manganite-cuprate system is investigated theoretically. We consider a situation in which spin-polarized electrons in manganite layers antiferromagnetically couple with electrons in cuprate layers as observed experimentally. The effect of the interfacial magnetic coupling is found to be much stronger than the injection of spin-polarized electrons into the cuprate region. As a result, the superconducting transition temperature depends on the thickness of the cuprate layer significantly. Since the magnetic coupling creates negative polarization, an applied magnetic field and the negative polarization compete, resulting in the inverse spin-switch behavior where the superconducting transition temperature is increased by applying a magnetic field.

  13. Liquid-gated superconductor-insulator transition in an electron-doped cuprate

    NASA Astrophysics Data System (ADS)

    Zeng, Shengwei; Huang, Zhen; Bao, Nina; Lv, Weiming; Liu, Zhiqi; Herng, T. S.; Gopinadhan, K.; Jian, Linke; Ding, J.; Venkatesan, T.; Ariando, Ariando

    2014-03-01

    Doping charge carriers will causes the change of cuprates from antiferromagnetic Mott insulators to high-Tc superconductors. Continuous changing of carrier density is necessary to understand the nature of such phase transition, and thus, further our understanding of cuprate superconductors. Electric field-effect doping, especially with electronic double layer transistors (EDLT) configuration which use ionic liquids (ILs) and polymer electrolyte as the gate dielectrics, is a potential avenue for this investigation and it has been shown its effectiveness in inducing phase transition in strongly correlated electron system. Owing to EDLT, superconductor-to-insulator transition (SIT) has been observed in hole-doped cuprates La2-xSrxCuO4 and YBa2Cu3Oy. Here we use EDLT to tune the carrier density in electron-doped cuprates Pr2-xCexCuO4 ultrathin films and cause the sample evolves from a superconducting state to an insulating state. This present results could be helpful to study SIT between electron- and hole-doped cuprates.

  14. Fermiology of the Undoped Cuprate Superconductor Pr2CuO4

    NASA Astrophysics Data System (ADS)

    McDonald, Ross; Breznay, Nicholas; Krockenberger, Yoshiharu; Modic, Kimberly; Zhu, Zengwei; Hayes, Ian; Nair, Nityan; Helm, Toni; Irie, Hiroshi; Yamamoto, Hideki; Analytis, James

    Unconventional, high temperature superconductivity consistently appears in the vicinity of suppressed phase transitions, leading to the suggestion that quantum criticality is vital to the physics of these systems. A confounding factor in identifying the role of quantum criticality in the electron-doped cuprates is the competing influence of chemical doping and oxygen stoichiometry. Recent advances in molecular beam epitaxy and preparation of cuprate thin films indicate that annealing can be employed to optimize Tc via the control of apical oxygen occupancy. For Pr2CuO4+/-δ the resulting square planar coordinated structure exhibits a 25 K superconducting transition in the absence of Cerium doping. Using these films and ultra high magnetic fields (>90 T) enables measurements of magnetic quantum oscillations - the first observation of their kind for a cuprate thin film. The oscillation frequency is consistent with the reconstructed Fermi surface of the bulk electron-doped cuprate Nd2-xCexCuO4. Furthermore, we observe a mass enhancement, suggesting that tuning these materials via oxygen stoichiometry enables exploration of underlying quantum criticality, providing a new axis with which to explore the physics underlying the electron doped side of the cuprate phase diagram.

  15. Unraveling electronic and magnetic structure at cuprate-manganite interfaces

    NASA Astrophysics Data System (ADS)

    Freeland, John

    2014-03-01

    Oxide interfaces offer a rich variety of physics and a pathway to create new classes of functional oxide materials. The interface between the cuprate high-temperature superconductors and ferromagnetic manganites is of particular interest due to the strongly antagonistic nature of the superconducting and ferromagnetic phases. Advancements in the synthesis of oxide heterostructure offers the opportunity to merge these two dissimilar oxides with atomic precision to understand the fundamental limits of bringing such states into close proximity. However, the main challenge is to understand the physical framework that describes the behavior of strongly correlated electrons near oxide interfaces. One aspect that will be addressed here is the use of advanced tools to gain detailed electronic and magnetic information from the boundary region. In this talk, recent work will be addressed both in connection to visualizing the interface with spatially resolved tools as well as harnessing layer-by-layer growth to explore the limits in ultrathin superlattices. These insights allow us to better understand the physics behind the interfacial spin and orbital reconstruction observed in this system. Work at Argonne is supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

  16. Infrared pseudogap in cuprate and pnictide high-temperature superconductors

    SciTech Connect

    Moon, S. J.; Lee, Y. S.; Schafgans, A. A.; Chubukov, A. V.; Kasahara, S.; Shibauchi, T.; Terashima, T.; Matsuda, Y.; Tanatar, M. A.; Prozorov, R.; Thaler, A.; Canfield, Paul C.; Bud'ko, Sergey L.; Sefat, A. S.; Mandrus, D.; Segawa, K.; Ando, Y.; Basov, D. N.

    2014-07-01

    We investigate infrared manifestations of the pseudogap in the prototypical cuprate and pnictide superconductors, YBa2Cu3Oy and BaFe2As2 (Ba122) systems. We find remarkable similarities between the spectroscopic features attributable to the pseudogap in these two classes of superconductors. The hallmarks of the pseudogap state in both systems include a weak absorption feature at about 500cm-1 followed by a featureless continuum between 500 and 1500cm-1 in the conductivity data and a significant suppression in the scattering rate below 700–900 cm-1. The latter result allows us to identify the energy scale associated with the pseudogap ΔPG. We find that in the Ba122-based materials the superconductivity-induced changes of the infrared spectra occur in the frequency region below 100–200 cm-1, which is much lower than the energy scale of the pseudogap. We performed theoretical analysis of the scattering rate data of the two compounds using the same model, which accounts for the effects of the pseudogap and electron-boson coupling. We find that the scattering rate suppression in Ba122-based compounds below ΔPG is solely due to the pseudogap formation, whereas the impact of the electron-boson coupling effects is limited to lower frequencies. The magnetic resonance modes used as inputs in our modeling are found to evolve with the development of the pseudogap, suggesting an intimate correlation between the pseudogap and magnetism

  17. Electronic excitations in electron-doped cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Unger, P.; Fulde, P.

    1995-04-01

    We calculate the electronic single-particle spectrum of an electron-doped cuprate superconductor such as Nd2-xCexCuO4-y. The dynamics of holes in the Cu-O planes is described by the extended Hubbard or Emery model. We consider the system at half-filling (one hole per unit cell, nh=1) and in the case of electron doping where the ground state is paramagnetic. The projection technique of Mori and Zwanzig is applied to derive the equations of motion for the Green's functions of Cu and O holes. These equations are solved self-consistently as in a previous calculation, where we considered the case of hole doping. At half-filling the system exhibits a charge-transfer gap bounded by Zhang-Rice singlet states and the upper Hubbard band. Upon electron doping the upper Hubbard band crosses the Fermi level and the system becomes metallic. With increasing electron doping the singlet band loses intensity and finally vanishes for nh=0. The corresponding spectral weight is transferred to the upper Hubbard band, which becomes a usual tight-binding band for zero hole concentration. The shape of the flat band crossing the Fermi level fits well to angle-resolved photoemission spectra of Nd2-xCexCuO4-y for x=0.15 and 0.22. Furthermore, our findings are in excellent agreement with exact diagonalization studies of 2×2 CuO2 cluster with periodic boundary conditions.

  18. Theoretical Modeling of Various Spectroscopies for Cuprates and Topological Insulators

    NASA Astrophysics Data System (ADS)

    Basak, Susmita

    Spectroscopies resolved highly in momentum, energy and/or spatial dimensions are playing an important role in unraveling key properties of wide classes of novel materials. However, spectroscopies do not usually provide a direct map of the underlying electronic spectrum, but act as a complex 'filter' to produce a 'mapping' of the underlying energy levels, Fermi surfaces (FSs) and excitation spectra. The connection between the electronic spectrum and the measured spectra is described as a generalized 'matrix element effect'. The nature of the matrix element involved differs greatly between different spectroscopies. For example, in angle-resolved photoemission (ARPES) an incoming photon knocks out an electron from the sample and the energy and momentum of the photoemitted electron is measured. This is quite different from what happens in K-edge resonant inelastic X-ray scattering (RIXS), where an X-ray photon is scattered after inducing electronic transitions near the Fermi energy through an indirect second order process, or in Compton scattering where the incident X-ray photon is scattered inelastically from an electron transferring energy and momentum to the scattering electron. For any given spectroscopy, the matrix element is, in general, a complex function of the phase space of the experiment, e.g. energy/polarization of the incoming photon and the energy/momentum/spin of the photoemitted electron in the case of ARPES. The matrix element can enhance or suppress signals from specific states, or merge signals of groups of states, making a good understanding of the matrix element effects important for not only a robust interpretation of the spectra, but also for ascertaining optimal regions of the experimental phase space for zooming in on states of the greatest interest. In this thesis I discuss a comprehensive scheme for modeling various highly resolved spectroscopies of the cuprates and topological insulators (TIs) where effects of matrix element, crystal

  19. Quantum Phase Transitions of Antiferromagnets and the Cuprate Superconductors

    NASA Astrophysics Data System (ADS)

    Sachdev, Subir

    I begin with a proposed global phase diagram of the cuprate superconductors as a function of carrier concentration, magnetic field, and temperature, and highlight its connection to numerous recent experiments. The phase diagram is then used as a point of departure for a pedagogical review of various quantum phases and phase transitions of insulators, superconductors, and metals. The bond operator method is used to describe the transition of dimerized antiferromagnetic insulators between magnetically ordered states and spin-gap states. The Schwinger boson method is applied to frustrated square lattice antiferromagnets: phase diagrams containing collinear and spirally ordered magnetic states, Z_2 spin liquids, and valence bond solids are presented, and described by an effective gauge theory of spinons. Insights from these theories of insulators are then applied to a variety of symmetry breaking transitions in d-wave superconductors. The latter systems also contain fermionic quasiparticles with a massless Dirac spectrum, and their influence on the order parameter fluctuations and quantum criticality is carefully discussed. I conclude with an introduction to strong coupling problems associated with symmetry breaking transitions in two-dimensional metals, where the order parameter fluctuations couple to a gapless line of fermionic excitations along the Fermi surface.

  20. Sun Oven Grown Cuprates Superconductivity and Periodic Lattice Distortions PLD

    NASA Astrophysics Data System (ADS)

    Acrivos, Juana V.; Chidvinadze, J. G.; Gulanova, D. D.; Loy, D.

    2011-03-01

    Bi 1.7 Pb 0.3 Sr 2 Ca n-1 Cu n O4 + 2 n + δ identified by the layer heavy element composition with substitution, s (2 s :2:n-1:n > 2) cuprates grown by green chemistry, transition temperatures to superconductivity Tc = 87 to 150K are related to their structure. Enhanced XRD at energies near but below the Cu K, and Pb and Bi L3-edges for pure n=2, 3 phases show Darwin shaped preferred [HKL] reflections that identify the magnitude of the allowed transition moment from the core state to extended unoccupied states determined by the electron density symmetry in that plane, confirmed by XAS of 3 μ m thick films. Weak PLD are still detected, but the stability gained by substitution of Bi by Pb is the formation of nearly symmetric Pb8 cubes in (2s : 2 : 1 : 2)13 and (2s < formula > < ? TeX super-lattices. The preferred 2D [HKL] reflection planes play the same role in the chemical activity of 3D solids as the linear bonds do in molecular reactions, governed by scattering dependent on the electron density symmetry in their highest and lowest unoccupied states. Supported by US NSF, Dreyfus, DOE Laboratories SSRL-SLAC, STUC-Ukraine and Georgia NSF.

  1. Polar Kerr effect in high temperature cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Tewari, Sumanta; Sharma, Girish; Goswami, Pallab; Yakovenko, Victor; Chakravarty, Sudip

    A mechanism is proposed for the tantalizing evidence of polar Kerr effect in a class of high temperature superconductors-the signs of the Kerr angle from two opposite faces of the same sample are identical and magnetic field training is non-existent. The mechanism does not break global time reversal symmetry, as in an antiferromagnet, and results in zero Faraday effect. It is best understood in a phenomenological model of bilayer cuprates, such as YBCO, in which intra-bilayer tunneling nucleates a chiral d-density wave such that the individual layers have opposite chirality. Although the presentation is specific to the chiral d-density wave, the mechanism may be more general to any quasi-two-dimensional orbital antiferromagnet in which time reversal symmetry is broken in each plane, but not when averaged macroscopically. St and GS supported by AFOSR (FA9550-13-1-0045), PG supported by JQI-NSF-PFC, SC supported by NSF-DMR-1004520.

  2. Novel Superoxygenated Phases in Superconducting Cuprate Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Zhang, H.; Gauquelin, N.; Botton, G. A.; McMahon, C.; Hawthorn, D. G.; Wei, J. Y. T.

    The superconducting critical temperature (Tc) of hole-doped cuprates tends to increase with their lattice complexity, which is generally correlated with higher states of oxidation. For YBa2Cu3O7 - δ (YBCO-123), it is known that solid-state reaction in high-pressure oxygen can induce the formation of more complex and oxidized phases such as Y2Ba4Cu7O15 - δ (YBCO-247) and Y2Ba4Cu8O16 (YBCO-248). In this work, we apply this superoxygenation concept of material synthesis to nanoscale thin films which, owing to their large surface-to-volume ratio, are more thermodynamically reactive than bulk samples. Epitaxial thin films of YBCO-123 were grown by pulsed laser deposition on (La , Sr) (Al , Ta) O3 substrates, and post-annealed in up to 500 atm of oxygen at 800C. Our post-annealed films show robust superconducting transitions with Tc ranging from 80 to 93K. Transmission electron microscopy and X-ray absorption spectroscopy were used to probe the lattice structure and oxygen stoichiometry. Our measurements show clear evidence of conversion to YBCO-247 and YBCO-248 in the superoxygenated films, as well as YBCO-125, a novel YBCO phase that has three CuO chains per unit cell and potentially higher Tc. Work supported by NSERC, CFI/OIT, and CIFAR.

  3. Infrared Faraday Measurements on Cuprate High Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Arik, M. Murat; Mukherjee, Alok; Cerne, John; Lubashevsky, Y.; Pan, Lidong; Armitage, N. P.; Kirzhner, T.; Koren, G.

    2014-03-01

    Recent measurements on cuprate high temperature superconductors (CHTS) have observed evidence for symmetry breakings in the pseudogap phase, suggesting that this is a full-fledged phase with an actual broken symmetry. To test the spectral character of this broken symmetry, we have made infrared polarization-sensitive measurements in the absence of magnetic field on a series of CHTS films. We have studied the Faraday effect (change in the polarization of transmitted light) in CHTS films as a function of temperature (10-300K), energy (0.1-3 eV), and sample orientation with respect to the incident light polarization. We observe a strong linear optical anisotropy, well above the superconducting transition temperature. This signal is maximized when the sample lattice axes are oriented near 45o with respect to the incident light polarization, and varies as the sample is rotated. We explore the temperature and energy dependence of this signal. This work supported by NSF-DMR1006078 and Gordon and Betty Moore Foundation through Grant GBMF2628.

  4. High Temperature Electrical Properties and Defect Structures of Alkaline Earth-Doped Lanthanum Cuprate Superconductors.

    NASA Astrophysics Data System (ADS)

    Shen, Li.

    1995-01-01

    Existing oxygen nonstoichiometry data of rm La_{2-x}Ba_{x}CuO _{4-y} and rm La _{2-x}Sr_{x}CuO_ {4-y} have been fitted by defect structure models featuring isolated oxygen vacancies, neutral associates and singly charged associates, respectively. The associate models fit the data acceptably well up to x = 0.4 while the isolated vacancy model does not fit the data as satisfactorily. Therefore, the oxygen deficiency in both systems is attributed to dopant-vacancy associates rather than isolated oxygen vacancies. However, all three models are unable to reproduce the flattening of electrical properties at high doping levels. Jonker plots reveal that the flattening is caused by degeneracy. The oxygen partial pressure dependence of the electrical properties indicates that the associates are not neutral but singly charged. Thermoelectric power and electrical conductivity have been measured in situ for rm La_ {2-x}Ca_{x}CuO_{4 -y} with x = 0-0.16 in P(O_2 ) = 10^{-5} { -1} atm at T = 700-1000^circ C. The results are similar to those of rm La_{2-x}Ba_{x}CuO _{4-y} and rm La _{2-x}Sr_{x}CuO_ {4-y} yet significant magnitudes of oxygen deficiency reportedly occur in rm La_ {2-x}Ca_{x}CuO_{4 -y} at much lower doping levels. Defect structure models involving charged oxygen vacancies cannot simultaneously fit both properties. Neutral oxygen vacancies and their association with dopants were invoked to reconcile both electrical property and oxygen nonstoichiometry data. The proposed defect structure models have been rationalized based on the bond-length mismatch first observed by Goodenough and his coworkers. The Cu-O bonds in the CuO_2 layers are longer than the La-O bonds in the (LaO)_2 layers. Substitution of larger Ba or Sr for La relieves the mismatch by lengthening the La-O bonds. Holes created for charge compensation contribute to the relief by shortening the Cu-O bonds. Once the mismatch is completely relieved, charged oxygen vacancies are formed in the (LaO)_2 layers, to minimize further expansions. The electrostatic attraction leads to the association of oppositely charged dopants and vacancies. Substitution of smaller Ca for La aggravates the mismatch by further shortening the La-O bonds. Neutral oxygen vacancies, together with holes, form in the CuO _2 layers to shorten Cu-O bonds to compensate the shortening of the La-O bonds. The association of dopants and vacancies can be explained by the preference of Ca for eight-fold coordination.

  5. Transport anomalies and quantum criticality in electron-doped cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Yu, Heshan; He, Ge; Hu, Wei; Yuan, Jie; Zhu, Beiyi; Jin, Kui

    2016-06-01

    Superconductivity research is like running a marathon. Three decades after the discovery of high-Tc cuprates, there have been mass data generated from transport measurements, which bring fruitful information. In this review, we give a brief summary of the intriguing phenomena reported in electron-doped cuprates from the aspect of electrical transport as well as the complementary thermal transport. We attempt to sort out common features of the electron-doped family, e.g. the strange metal, negative magnetoresistance, multiple sign reversals of Hall in mixed state, abnormal Nernst signal, complex quantum criticality. Most of them have been challenging the existing theories, nevertheless, a unified diagram certainly helps to approach the nature of electron-doped cuprates.

  6. Interpretation of scanning tunneling quasiparticle interference and impurity states in cuprates.

    PubMed

    Kreisel, A; Choubey, Peayush; Berlijn, T; Ku, W; Andersen, B M; Hirschfeld, P J

    2015-05-29

    We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi_{2}Sr_{2}CaCu_{2}O_{8} can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude "filter" theories on a microscopic foundation and solves a long-standing puzzle. We then study quasiparticle interference phenomena induced by out-of-plane weak potential scatterers, and show how patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging. PMID:26066452

  7. Infrared conductivity of cuprates using Yang-Rice-Zhang ansatz: Review of our recent investigations

    SciTech Connect

    Singh, Navinder; Sharma, Raman

    2015-05-15

    A review of our recent investigations related to the ac transport properties in the psedogapped state of cuprate high temperature superconductors is presented. For our theoretical calculations we use a phenomenological Green’s function proposed by Yang, Rice and Zhang (YRZ). This is based upon the renormalized mean-field theory of the Hubbard model and takes into account the strong electron-electron interaction present in Cuprates. The pseudogap is also taken into account through a proposed self energy. We have tested the form of the Green’s function by computing ac conductivity of cuprates and then compared with experimental results. We found agreement between theory and experiment in reproducing the doping evolution of ac conductivity but there is a problem with absolute magnitudes and their frequency dependence. This shows a partial success of the YRZ ansatz. The ways to rectify it are suggested and worked out.

  8. Itinerant effects and enhanced magnetic interactions in Bi-based multilayer cuprates

    SciTech Connect

    Dean, M. P. M.; James, A. J. A.; Walters, A. C.; Bisogni, V.; Jarrige, I.; Hücker, M.; Giannini, E.; Fujita, M.; Pelliciari, J.; Huang, Y. B.; Konik, R. M.; Schmitt, T.; Hill, J. P.

    2014-12-04

    The cuprate high temperature superconductors exhibit a pronounced trend in which the superconducting transition temperature, T c, increases with the number of CuO₂ planes, n, in the crystal structure. We compare the magnetic excitation spectrum of Bi₂₊xSr₂₋xCuO₆+δ (Bi-2201) and Bi₂Sr₂Ca₂Cu₃O₁₀₊δ (Bi-2223), with n = 1 and n = 3 respectively, using Cu L₃-edge resonant inelastic x-ray scattering (RIXS). Near the anti-nodal zone boundary we find the paramagnon energy in Bi-2223 is substantially higher than that in Bi-2201, indicating that multilayer cuprates host stronger effective magnetic exchange interactions, providing a possible explanation for the Tc vs. n scaling. In contrast, the nodal direction exhibits very strongly damped, almost non-dispersive excitations. As a result, we argue that this implies that the magnetism in the doped cuprates is partially itinerant in nature.

  9. Strain-controlled critical temperature in REBa2Cu3Oy-coated conductors

    PubMed Central

    Awaji, Satoshi; Suzuki, Takumi; Oguro, Hidetoshi; Watanabe, Kazuo; Matsumoto, Kaname

    2015-01-01

    Recently, we succeeded in detwinning REBa2Cu3O7 (RE123, RE = rare-earth elements)-coated conductors by annealing under an external uniaxial strain. Using the untwinned RE123 tapes, the uniaxial-strain dependencies of the critical temperature Tc along the a and b crystal axes were investigated over a wide strain region from compression to tension. We found that the strain dependencies of Tc for the a and b axes obey a power law but exhibit opposite slopes. In particular, the maximum value of Tc is obtained when the CuO2 plane becomes a square, and its lattice constant is close to 0.385 nm. It is suggested that a tetragonal structure with a ≈ 0.385 nm is the optimum condition for a high critical temperature in high-Tc cuprates. PMID:26063123

  10. Strain-controlled critical temperature in REBa2Cu3Oy-coated conductors.

    PubMed

    Awaji, Satoshi; Suzuki, Takumi; Oguro, Hidetoshi; Watanabe, Kazuo; Matsumoto, Kaname

    2015-01-01

    Recently, we succeeded in detwinning REBa2Cu3O7 (RE123, RE = rare-earth elements)-coated conductors by annealing under an external uniaxial strain. Using the untwinned RE123 tapes, the uniaxial-strain dependencies of the critical temperature Tc along the a and b crystal axes were investigated over a wide strain region from compression to tension. We found that the strain dependencies of Tc for the a and b axes obey a power law but exhibit opposite slopes. In particular, the maximum value of Tc is obtained when the CuO2 plane becomes a square, and its lattice constant is close to 0.385 nm. It is suggested that a tetragonal structure with a ≈ 0.385 nm is the optimum condition for a high critical temperature in high-Tc cuprates. PMID:26063123

  11. Doping-dependent charge order correlations in electron-doped cuprates

    PubMed Central

    da Silva Neto, Eduardo H.; Yu, Biqiong; Minola, Matteo; Sutarto, Ronny; Schierle, Enrico; Boschini, Fabio; Zonno, Marta; Bluschke, Martin; Higgins, Joshua; Li, Yangmu; Yu, Guichuan; Weschke, Eugen; He, Feizhou; Le Tacon, Mathieu; Greene, Richard L.; Greven, Martin; Sawatzky, George A.; Keimer, Bernhard; Damascelli, Andrea

    2016-01-01

    Understanding the interplay between charge order (CO) and other phenomena (for example, pseudogap, antiferromagnetism, and superconductivity) is one of the central questions in the cuprate high-temperature superconductors. The discovery that similar forms of CO exist in both hole- and electron-doped cuprates opened a path to determine what subset of the CO phenomenology is universal to all the cuprates. We use resonant x-ray scattering to measure the CO correlations in electron-doped cuprates (La2−xCexCuO4 and Nd2−xCexCuO4) and their relationship to antiferromagnetism, pseudogap, and superconductivity. Detailed measurements of Nd2−xCexCuO4 show that CO is present in the x = 0.059 to 0.166 range and that its doping-dependent wave vector is consistent with the separation between straight segments of the Fermi surface. The CO onset temperature is highest between x = 0.106 and 0.166 but decreases at lower doping levels, indicating that it is not tied to the appearance of antiferromagnetic correlations or the pseudogap. Near optimal doping, where the CO wave vector is also consistent with a previously observed phonon anomaly, measurements of the CO below and above the superconducting transition temperature, or in a magnetic field, show that the CO is insensitive to superconductivity. Overall, these findings indicate that, although verified in the electron-doped cuprates, material-dependent details determine whether the CO correlations acquire sufficient strength to compete for the ground state of the cuprates. PMID:27536726

  12. Doping-dependent charge order correlations in electron-doped cuprates.

    PubMed

    da Silva Neto, Eduardo H; Yu, Biqiong; Minola, Matteo; Sutarto, Ronny; Schierle, Enrico; Boschini, Fabio; Zonno, Marta; Bluschke, Martin; Higgins, Joshua; Li, Yangmu; Yu, Guichuan; Weschke, Eugen; He, Feizhou; Le Tacon, Mathieu; Greene, Richard L; Greven, Martin; Sawatzky, George A; Keimer, Bernhard; Damascelli, Andrea

    2016-08-01

    Understanding the interplay between charge order (CO) and other phenomena (for example, pseudogap, antiferromagnetism, and superconductivity) is one of the central questions in the cuprate high-temperature superconductors. The discovery that similar forms of CO exist in both hole- and electron-doped cuprates opened a path to determine what subset of the CO phenomenology is universal to all the cuprates. We use resonant x-ray scattering to measure the CO correlations in electron-doped cuprates (La2-x Ce x CuO4 and Nd2-x Ce x CuO4) and their relationship to antiferromagnetism, pseudogap, and superconductivity. Detailed measurements of Nd2-x Ce x CuO4 show that CO is present in the x = 0.059 to 0.166 range and that its doping-dependent wave vector is consistent with the separation between straight segments of the Fermi surface. The CO onset temperature is highest between x = 0.106 and 0.166 but decreases at lower doping levels, indicating that it is not tied to the appearance of antiferromagnetic correlations or the pseudogap. Near optimal doping, where the CO wave vector is also consistent with a previously observed phonon anomaly, measurements of the CO below and above the superconducting transition temperature, or in a magnetic field, show that the CO is insensitive to superconductivity. Overall, these findings indicate that, although verified in the electron-doped cuprates, material-dependent details determine whether the CO correlations acquire sufficient strength to compete for the ground state of the cuprates. PMID:27536726

  13. Diamagnetism of real-space pairs above T(c) in hole doped cuprates.

    PubMed

    Alexandrov, A S

    2010-10-27

    The nonlinear normal state diamagnetism reported by Li et al (2010 Phys. Rev. B 81 054510) is shown to be incompatible with a claimed Cooper pairing and vortex liquid above the resistive critical temperature. However, it is perfectly compatible with the normal state Landau diamagnetism of real-space composed bosons, which provides a description of the nonlinear magnetization curves of the less anisotropic cuprates La-Sr-Cu-O (LSCO) and Y-Ba-Cu-O (YBCO) as well as for strongly anisotropic bismuth-based cuprates over the whole range of available magnetic fields. PMID:21403318

  14. Interlayer coupling and the thermopower of cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Zhou, J.-S.; Goodenough, J. B.

    1996-11-01

    A review of the extant literature on the thermopower (TEP) of the cuprate superconductors reveals a transition from polaronic to homogeneous itinerant electron behavior with increasing hole concentration in the CuO2 sheets. Superconductivity appears at the compositions of crossover from one regime to the other, and the normal state of the superconductors retains a heterogeneous electronic structure of mobile hole-rich and hole-poor domains, which introduces both a statistical and a transport component to the Seebeck coefficient. A primary manifestation of the transport component is an enhancement term δα(T) having a maximum at a Tmax=100-140 K, which is characteristic of a strong coupling of the charge carriers to optical rather than acoustic phonons. Comparison of the TEP for La1.85Sr0.15CuO4 vs La0.85Sr1.15GaCuO5 and La1.8Sr0.2CaCu2O6+δ vs Bi2Sr2CaCu2O8+δ indicates that an increase in the c-axis coupling between neighboring CuO2 sheets increases the size of the polaron or hole-rich domains in the underdoped compositions, thereby lowering the room-temperature value of the Seebeck coefficient α(300 K) and increasing the magnitude of δα(T). These observations implicate a strong elastic component, enhanced by electron-lattice interactions, in the c-axis coupling as well as in the formation of larger nonadiabatic polarons and their interactions within the CuO2 planes. They also signal that caution must be exercised in any application of a ``universal plot'' of α(300 K) versus hole concentration p per Cu atom in a CuO2 plane to obtain a value of p from TEP data.

  15. Tuning order in the cuprate superconductors by a magnetic field

    NASA Astrophysics Data System (ADS)

    Sachdev, Subir

    2002-03-01

    An innovative series of recent neutron scattering(B. Lake et al.), Science 291, 1759 (2001); B. Khyakovich et al., preprint; B. Lake et al., preprint. and STM(J. Hoffman et al.), Science, Feb 2002. experiments have shed new light on the nature of strong correlations in the cuprate superconductors. Some of these experiments use a magnetic field, applied perpendicular to the CuO2 layers, to tune the low temperature properties of the superconducting state. Their results support the idea that ground state correlations in the doped Mott insulator can be described using a framework of competing order parameters, and of proximity to quantum phase transitions associated with them. In our view, they also offer compelling evidence that the orders competing with superconductivity are spin and charge density waves. The predictions(E. Demler, S. Sachdev, and Y. Zhang, Phys. Rev. Lett. 87), 067202 (2001); S. Sachdev, cond- mat/0108238 A. Polkovnikov, S. Sachdev, M. Vojta, and E. Demler, cond- mat/0110329. of the theories of such quantum transitions will be reviewed and compared with the recent experimental results. In particular, we show that the quantum theory of a spin-density-wave ordering transition in a superconductor simultaneously describes a variety of observations with a single set of typical parameters: the field dependence of the elastic neutron scattering intensity, the absence of satellite Bragg peaks associated with the vortex lattice in existing neutron scattering experiments, and the spatial extent of the charge order in STM experiments.

  16. Angle-Resolved Photoemission Spectroscopy on Electronic Structure and Electron-Phonon Coupling in Cuprate Superconductors

    SciTech Connect

    Zhou, X.J.

    2010-04-30

    In addition to the record high superconducting transition temperature (T{sub c}), high temperature cuprate superconductors are characterized by their unusual superconducting properties below T{sub c}, and anomalous normal state properties above T{sub c}. In the superconducting state, although it has long been realized that superconductivity still involves Cooper pairs, as in the traditional BCS theory, the experimentally determined d-wave pairing is different from the usual s-wave pairing found in conventional superconductors. The identification of the pairing mechanism in cuprate superconductors remains an outstanding issue. The normal state properties, particularly in the underdoped region, have been found to be at odd with conventional metals which is usually described by Fermi liquid theory; instead, the normal state at optimal doping fits better with the marginal Fermi liquid phenomenology. Most notable is the observation of the pseudogap state in the underdoped region above T{sub c}. As in other strongly correlated electrons systems, these unusual properties stem from the interplay between electronic, magnetic, lattice and orbital degrees of freedom. Understanding the microscopic process involved in these materials and the interaction of electrons with other entities is essential to understand the mechanism of high temperature superconductivity. Since the discovery of high-T{sub c} superconductivity in cuprates, angle-resolved photoemission spectroscopy (ARPES) has provided key experimental insights in revealing the electronic structure of high temperature superconductors. These include, among others, the earliest identification of dispersion and a large Fermi surface, an anisotropic superconducting gap suggestive of a d-wave order parameter, and an observation of the pseudogap in underdoped samples. In the mean time, this technique itself has experienced a dramatic improvement in its energy and momentum resolutions, leading to a series of new discoveries not

  17. Origin of dz2 orbital suppression of d-wave superconductive pairs in cuprate

    NASA Astrophysics Data System (ADS)

    Tang, Huai Bao; Li, Guang; Zhang, Hai Jun; Zuo, Xue Qin; Meng, Fan Ming; Liu, Da Yong

    2015-07-01

    Compared to Hg-cuprate, the origin that the dz2 orbital suppresses the d-wave superconductive (SC) pairs in La-cuprate is studied based on an effective two-orbital t-J-U model by using the Kotliar-Ruckenstein (KR) slave-boson technique. By analyzing the orbital-dependent electron distribution, it is elaborated that the double occupancy of dx2-y2 orbital, caused by the dz2 orbital mixture, should be responsible for the suppression of the d-wave SC pairs in La-cuprate. When the Coulomb interaction U increases, the ground state hosting the large double occupancy of dx2-y2 orbital in La-cuprate is stabilized by the localization of the carriers due to the Coulomb-blocking instead of reducing the double occupancy by the way of lowering of Coulomb potential energy. Therefore, it could be concluded that the mechanism that the double occupancy destructs against d-wave SC pairs is robust even if the strong Coulomb interaction exists in the La-based compounds.

  18. Neutron scattering studies on stripe phases in non-cuprate materials

    NASA Astrophysics Data System (ADS)

    Ulbrich, Holger; Braden, Markus

    2012-11-01

    Several non-cuprates layered transition-metal oxides exhibit clear evidence for stripe ordering of charges and magnetic moments. Therefore, stripe order should be considered as the typical consequence of doping a layered Mott insulator, but only in cuprates stripe order or fluctuating stripes coexist with metallic properties. A linear relationship between the charge concentration and the incommensurate structural and magnetic modulations can be considered as the finger print of stripe ordering with localized degrees of freedom. In nickelates and in cobaltates with K2NiF4 structure, doping suppresses the nearest-neighbor antiferromagnetism and induces stripe order. The higher amount of doping needed to induce stripe phases in these non-cuprates series can be attributed to reduced charge mobility. Also manganites exhibit clear evidence for stripe phases with further enhanced complexity, because orbital degrees of freedom are involved. Orbital ordering is the key element of stripe order in manganites since it is associated with the strongest structural distortion and with the perfectly fulfilled relation between doping and incommensurability. Magnetic excitations in insulating stripe phases exhibit strong similarity with those in the cuprates, but only for sufficiently short magnetic correlation lengths reflecting well-defined magnetic stripes that are only loosely coupled.

  19. Excitation of coherent oscillations in underdoped cuprate superconductors by intense THz pulses

    NASA Astrophysics Data System (ADS)

    Hoffmann, Matthias C.; Lee, Wei-Sheng; Dakovski, Georgi L.; Turner, Joshua J.; Gerber, Simon M.; Bonn, Doug; Hardy, Walter; Liang, Ruixing; Salluzzo, Marco

    2016-05-01

    We use intense broadband THz pulses to excite the cuprate superconductors YBCO and NBCO in their underdoped phase, where superconducting and charge density wave ground states compete. We observe pronounced coherent oscillations at attributed to renormalized low-energy phonon modes. These oscillation features are much more prominent than those observed in all-optical pump-probe measurements, suggesting a different excitation mechanism.

  20. Spin excitations and superconductivity in cuprate oxide and heavy electron superconductors

    NASA Astrophysics Data System (ADS)

    Pines, David

    1990-04-01

    The experimental evidence for a temperature-dependent build up of antiferromagnetic correlations between Cu 2+ planar spins in the normal state of cuprate oxide superconductors is reviewed, and a phenomenological one-component model, developed in collaboration with A. Millis and H. Monien, which appears capable of providing a quantitative account of existing experiments is described. A scaling law which relates the superconducting transaction temperature to the measurable spin-spin correlation length is proposed. The NMR experimental results in the superconducting state are shown to be consistent with d-wave pairing in a strong coupling superconductor. Comparison of the results of NMR experiments on the cuprate oxide and heavy electron superconductors reveals striking similarities. I conclude that the cuprate oxide superconductors are unconventional superconductors in which the superconductivity is of (primarily) electronic origin and results from an attractive interaction of antiferromagnetic character between itinerant quasiparticles in the spin antisymmetric channel, and discuss similarities and differences between cuprate oxide and heavy electron systems.

  1. Quantized massive collective modes and massive spin fluctuations in high-Tc cuprates

    NASA Astrophysics Data System (ADS)

    Kanazawa, I.; Sasaki, T.

    2015-10-01

    We have analyzed angle-resolved photoemission spectra of the single- and double-layered Bi-family high-Tc superconductors by using quantized massive gauge fields, which might contain effects of spin fluctuations, charge fluctuations, and phonons. It is suggested strongly that the quantized massive gauge fields might be mediating Cooper pairing in high-Tc cuprates.

  2. Nuclear Magnetic Resonance and High-Temperature Superconductivity in YTTRIUM(1-X)PRASEODYMIUM(X)BARIUM Cuprate

    NASA Astrophysics Data System (ADS)

    Reyes, Arneil Payongayong

    Copper nuclear magnetic resonance (NMR) has been performed on praseodymium-doped YBa_2Cu _3O_7, to investigate the nature of the depression of the superconducting transition temperature T_{c} with Pr concentration in this series and to provide insight into the microscopic and magnetic properties of high T_{c } planar cuprate materials. Praseodymium is unique among rare-earth dopants in suppressing superconductivity in the high T _{c} cuprate YBa _2Cu_3O_7 while maintaining the orthorhombic structure of the host. Temperature dependence of the Knight shift K and the nuclear relaxation rate 1/T_1 has been observed in Y-rich Y_{1-x}Pr _ xBa_2Cu _3O_7. Its striking resemblance to the behavior found in oxygen deficient YBa_2Cu_3O _{7-y} provides evidence that T_{c} depression in the former is primarily due to the removal of hole carriers as a consequence of Pr being close to tetravalent state. This hole-filling mechanism is consistent with the observed antiferromagnetic ordering of Cu spins on the plane sites in both PrBa_2Cu_3O_7 and YBa_2Cu_3O_6 since the absence of the doped-holes on the Cu -O_2 planes enhances spin correlations among Cu local moments. On the other hand, extensive analysis of the spin susceptibility has shown a tendency towards trivalency of Pr in specimens with low x values, suggesting that in the dilute limit pair-breaking due to conduction band-4f hybridization is also involved in the depression of T_{c}. The mixed-valent nature of Pr must therefore be considered for any adequate explanation of the suppression of superconductivity in Y_{1-x}Pr_ xBa_2Cu_3 O_7. The phenomenological model of antiferromagnetic Fermi liquid (AFL) proposed by Millis, Monien and Pines has been used to explain the behavior of the planar ^{63}Cu relaxation rate and to extract information on the strength of correlations among the local spins. Analysis has shown that the unusual behavior of the relaxation rate is a consequence of a competition between the temperature

  3. Optical Properties of Doped Cuprates and Related Materials

    NASA Astrophysics Data System (ADS)

    Yoon, Young-Duck

    1995-01-01

    The optical properties of cuprates, rm Nd_{2-it x}Ce_{it x}CuO_4 and rm La_ {2-it x}Sr_{it x}CuO _4, and the related materials, rm Ba_{1-it x}K_{it x}BiO_3 (BKBO) and rm BaPb_{1-it x}Bi_{1- it x}O_3 (BPBO), have been extensively investigated by doping- and temperature-dependent reflectance measurement of single crystal samples in the frequency range between 30 cm^{-1} (4 meV) and 40 000 cm^{-1} (5 eV). The rm Nd_{2-it x}Ce_{it x}CuO_4 system has been studied at Ce compositions in the range 0 <=q x <=q 0.2. rm La_{2-it x}Sr_{it x}CuO_4 has been studied in the spin glass doping regime, (x <=q 0.04). The two bismuthates have been investigated as superconducting materials with the maximum T_{c} . Our results for rm Nd_{2 -it x}Ce_{it x}CuO_4 show that doping with electrons induces a transfer of spectral weight from the high energy side above the charge transfer excitation band to the low energy side below 1.2 eV, similar to the results observed in hole-doped rm La_{2-it x}Sr_ {it x}CuO_4. However, the low frequency spectral weight grows slightly faster than 2x with doping x, as expected for the Mott-Hubbard model. We find very interesting results at low doping levels in rm La_{2-it x }Sr_{it x}CuO_4. Upon Sr doping the oscillator strength of the phonons is gradually reduced and doping induced modes (Raman modes and carrier-lattice interaction mode) appear in the far -infrared. We also find that the deformation potential by the dynamical tilting of CuO_6 octahedra induces a carrier-lattice interaction. The carrier -lattice interaction is characterized by strong infrared active modes and an appearance of the strong A _{g} Raman modes upon cooling. Finally, we present the normal and the superconducting properties of Bi-O superconductors. We conclude that the BKBO system is a weak- or moderate-coupling BCS-type superconductor in the dirty limit.

  4. Microwave Absorption and Low-Frequency AC Losses in 1-2-3 Cuprate Superconductors

    NASA Astrophysics Data System (ADS)

    Huang, Ming Xun

    We have studied various aspects of microwave absorption in cuprates of the prototype REBa_2Cu _3O_{rm x} (6 < x < 7), where RE stands for Y or a rare earth ion. The first series of experiments concern the discovery and subsequent elucidation of a huge increase in zero field microwave absorption, at temperatures below 20 K, in micron size powder samples of ErBa_2Cu _3O_{rm x}. The field dependence of the microwave absorption was used to show that this abnormal zero field signal is a part of a broad and highly distorted electron spin resonance (ESR) spectrum. Spectra at different frequencies were analyzed using the "weak exchange, strong dipole field" Kubo-Toyabe model for the first time and we conclude that there is a large (~1 kOe) fluctuating local dipolar field at the Er site coming from the other Er^{3+} magnetic moments. For better understanding, experiments were done on ESR in powders of Er_{rm x}Y _{rm 1-z}Ba_2 Cu_3O_6 (0.02 < z < 1). For z < 0.4, another partially resolved line appeared at low fields. These spectra cannot be described as a powder pattern due to a single line with an anisotropic g-value. Rather they appear to be the sum of two Kubo -Toyabe lines. Most likely these lines are resonances coming from two closely spaced (~1K) low lying doublets. Crystal field calculations indicate that the distortion away from cubic symmetry implied by our results is much smaller than that required to describe the results of neutron scattering measurements. Another series of experiments were done to measure the increase in the microwave absorption in thin films of YBa_2Cu_3O _7 due to the application of a dc magnetic field (B) between 0.45 and 1.4 Tesla at 0.8 < (T/Tc) < 1. The data are very well represented by conventional models of fluxon dynamics. We have also measured the real (chi _1) and imaginary (chi_2 ) parts of the low frequency (<150 Hz) complex ac susceptibility. It was found that the data can be understood by using the Bean model.

  5. Evolution of superconducting gap and metallic ground state in cuprates from transport

    NASA Astrophysics Data System (ADS)

    Taillefer, Louis

    2006-03-01

    We report on fundamental characteristics of the ground state of cuprates in the limit of T=0, for both normal and superconducting states, obtained from transport measurements on high-quality single crystals of YBCO and Tl-2201, as a function of hole concentration. The superconducting gap is extracted from thermal conductivity; it is found to scale with the superconducting transition temperature throughout the overdoped regime, with a gap-to-Tc ratio of 5 [1]. The normal state is accessed by suppressing superconductivity with magnetic fields up to 60 T and is characterized by the limiting behavior of its electrical resistivity; while carrier localization is observed in YBCO at low temperature for carrier concentrations p below 0.1 hole/planar Cu, at p=0.1 and above the material remains highly metallic down to T=0 [2]. This shows that the non-superconducting state of underdoped cuprates, deep in the pseudogap phase, is remarkably similar to that of strongly overdoped cuprates, e.g. at p=0.3. We compare these results with similar measurements on other cuprates and discuss their implication for our understanding of the cuprate phase diagram. [1] In collaboration with: D.G. Hawthorn, S.Y. Li, M. Sutherland, E. Boaknin, R.W. Hill, C. Proust, F. Ronning, M. Tanatar, J. Paglione, D. Peets, R. Liang, D.A. Bonn, W.N. Hardy, and N.N. Kolesnikov. [2] In collaboration with: C. Proust, M. Sutherland, N. Doiron- Leyraud, S.Y. Li, R. Liang, D.A. Bonn, W.N. Hardy, N.E. Hussey, S. Adachi, S. Tajima, J. Levallois, and M. Narbone.

  6. Atomic scale studies of doped-hole distributions, self-organized electronic nano-domains, and electron-boson coupling in high Tc-cuprates

    SciTech Connect

    Davis, James C.

    2014-05-14

    Progress is reported in these areas (titles and abstracts of journal articles produced for the contract): Exotic Density Wave in Underdoped Cuprates; Varying the inter-atomic distances within individual crystal unit-­cells of cuprates; Truncated Momentum Space Electronic Structure of Underdoped Bi2Sr2CaCu2O8+δ; and, Visualizing Phase Fluctuating d-Wave Superconductivity in the Cuprate Pseudogap State.

  7. Variable-range hopping theory for the gap observed in strongly underdoped cuprate Bi2Sr2 -xLaxCuO6 +δ

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Qiang; Zhang, Jun-Qiu; Rice, T. M.; Zhang, Fu-Chun

    2016-06-01

    Recent angle resolved photoemission spectroscopy experiments on strongly underdoped Bi2Sr2 -xLaxCuO6 +δ cuprates have reported an unusual gap in the nodal direction. Transport experiments on these cuprates observed variable-range hopping behavior. These cuprates have both electron and hole doping, which has led to proposals that this cuprate is analogous to partially compensated semiconductors. The nodal gap then corresponds to the Efros-Shklovskii (ES) gap in such semiconductors. We calculate the doping and temperature dependence of an ES gap model and find support for an Efros-Shklovskii model.

  8. Perspective on the phase diagram of cuprate high-temperature superconductors.

    PubMed

    Rybicki, Damian; Jurkutat, Michael; Reichardt, Steven; Kapusta, Czesław; Haase, Jürgen

    2016-01-01

    Universal scaling laws can guide the understanding of new phenomena, and for cuprate high-temperature superconductivity the influential Uemura relation showed, early on, that the maximum critical temperature of superconductivity correlates with the density of the superfluid measured at low temperatures. Here we show that the charge content of the bonding orbitals of copper and oxygen in the ubiquitous CuO2 plane, measured with nuclear magnetic resonance, reproduces this scaling. The charge transfer of the nominal copper hole to planar oxygen sets the maximum critical temperature. A three-dimensional phase diagram in terms of the charge content at copper as well as oxygen is introduced, which has the different cuprate families sorted with respect to their maximum critical temperature. We suggest that the critical temperature could be raised substantially if one were able to synthesize materials that lead to an increased planar oxygen hole content at the expense of that of planar copper. PMID:27150719

  9. Enhancement of superconductivity via periodic modulation in a three-dimensional model of cuprates

    NASA Astrophysics Data System (ADS)

    Raines, Zachary M.; Stanev, Valentin; Galitski, Victor M.

    2015-05-01

    Recent experiments in the cuprates have seen evidence of a transient superconducting state upon optical excitation polarized along the c axis [R. Mankowsky et al., Nature (London) 516, 71 (2014), 10.1038/nature13875]. Motivated by these experiments, we propose an extension of the single-layer t -J -V model of cuprates to three dimensions in order to study the effects of interplane tunneling on the competition between superconductivity and bond density wave order. We find that an optical pump can suppress the charge order and simultaneously enhance superconductivity, due to the inherent competition between the two. We also provide an intuitive picture of the physical mechanism underlying this effect. Furthermore, based on a simple Floquet theory, we estimate the magnitude of the enhancement.

  10. Strong-coupling superconductivity, the Lorenz number, and the Nernst effect in cuprates

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sasha

    2004-03-01

    Strong electron-phonon interaction in the cuprates has gathered support over the last decade in a large number of experiments. Here I argue that the bipolaron extension of the BCS theory to the strong-coupling regime [1] naturally explains the temperature dependent Lorenz number and the large Nernst effect in the cuprates. The Wiedemann-Franz law breaks down due to the interference of polaron and bipolaron contributions to the heat flow that provides a quantitative fit to the experimental "Hall" Lorenz number [2]. A strong enhancement of the Nernst signal and its magnetic field dependence above Tc originate in a critical slowing down of the bipolaron relaxation times, when the system approaches the Bose-Einstein condensation. [1] A.S. Alexandrov, Theory of superconductivity: from weak to strong coupling, IOP Publishing (Bristol-Philadelphia, 2003) [2] K. K. Lee, A. S. Alexandrov, and W. Y. Liang, Phys. Rev. Lett. 90, 217001 (2003)

  11. Berry phases and the intrinsic thermal Hall effect in high-temperature cuprate superconductors.

    PubMed

    Cvetkovic, Vladimir; Vafek, Oskar

    2015-01-01

    Bogolyubov quasiparticles move in a practically uniform magnetic field in the vortex state of high-temperature cuprate superconductors. When set in motion by an externally applied heat current, the quasiparticles' trajectories may bend, causing a temperature gradient perpendicular to the heat current and the applied magnetic field, resulting in the thermal Hall effect. Here we relate this effect to the Berry curvature of quasiparticle magnetic sub-bands, and calculate the dependence of the intrinsic thermal Hall conductivity on superconductor's temperature, magnetic field and the amplitude of the d-wave pairing. The intrinsic contribution to thermal Hall conductivity displays a rapid onset with increasing temperature, which compares favourably with existing experiments at high magnetic field on the highest purity samples. Because such temperature onset is related to the pairing amplitude, our finding may help to settle a much-debated question of the bulk value of the pairing strength in cuprate superconductors in magnetic field. PMID:25758469

  12. Comment on "Berry phase mechanism for optical gyrotropy in stripe-ordered cuprates"

    NASA Astrophysics Data System (ADS)

    Chakravarty, Sudip

    2014-02-01

    I comment on two recent papers on the Kerr effect as evidence of gyrotropic order in cuprates, and I suggest that the arguments may not be sound. The difficulty is that, in practically all cases, the wave vector kz perpendicular to the copper-oxygen plane is not a good quantum number. This appears to be problematic for Orenstein and Moore [Phys. Rev. B 87, 165110 (2013), 10.1103/PhysRevB.87.165110], whereas, in Hosur et al. [Phys. Rev. B 87, 115116 (2013), 10.1103/PhysRevB.87.115116], the symmetry arguments may turn out to be robust, but the microscopic picture is wanting. Thus, the Kerr effect in cuprates remains a puzzle as there is little doubt that the arguments presented against time-reversal symmetry breaking appear to be rather strong on experimental grounds in both of these papers.

  13. A pseudogap term in the magnetic response of the cuprate superconductors

    SciTech Connect

    Walstedt, Professor Russell E.; Mason, Dr. Thomas Edward; Aeppli, Professor Gabriel; Hayden, Professor Stephen M.; Mook Jr, Herbert A

    2011-01-01

    We combine neutron scattering (INS) data and NMR/NQR nuclear spin lattice relaxation rate (1/T1) data to deduce the existence of a new contribution to the magnetic response (~q, ) in cuprate superconductors. This contribution, which has yet to be observed with INS, is shown to embody the magnetic pseudogap effects. As such, it explains the long-standing puzzle of pseudogap effects missing from cuprate INS data, dominated by stripe fluctuations, for (~q, ) at low energies. For La1.86Sr0.14CuO4 and Y Ba2Cu3O6.5, the new term is the chief contributor to 1/T1 for T Tc.

  14. Perspective on the phase diagram of cuprate high-temperature superconductors

    PubMed Central

    Rybicki, Damian; Jurkutat, Michael; Reichardt, Steven; Kapusta, Czesław; Haase, Jürgen

    2016-01-01

    Universal scaling laws can guide the understanding of new phenomena, and for cuprate high-temperature superconductivity the influential Uemura relation showed, early on, that the maximum critical temperature of superconductivity correlates with the density of the superfluid measured at low temperatures. Here we show that the charge content of the bonding orbitals of copper and oxygen in the ubiquitous CuO2 plane, measured with nuclear magnetic resonance, reproduces this scaling. The charge transfer of the nominal copper hole to planar oxygen sets the maximum critical temperature. A three-dimensional phase diagram in terms of the charge content at copper as well as oxygen is introduced, which has the different cuprate families sorted with respect to their maximum critical temperature. We suggest that the critical temperature could be raised substantially if one were able to synthesize materials that lead to an increased planar oxygen hole content at the expense of that of planar copper. PMID:27150719

  15. Two-dimensional superconductor-insulator quantum phase transitions in an electron-doped cuprate

    NASA Astrophysics Data System (ADS)

    Zeng, S. W.; Huang, Z.; Lv, W. M.; Bao, N. N.; Gopinadhan, K.; Jian, L. K.; Herng, T. S.; Liu, Z. Q.; Zhao, Y. L.; Li, C. J.; Harsan Ma, H. J.; Yang, P.; Ding, J.; Venkatesan, T.; Ariando

    2015-07-01

    We use an ionic liquid-assisted electric-field effect to tune the carrier density in an electron-doped cuprate ultrathin film and cause a two-dimensional superconductor-insulator transition (SIT). The low upper critical field in this system allows us to perform magnetic-field (B)-induced SIT in the liquid-gated superconducting film. Finite-size scaling analysis indicates that SITs induced both by electric and by magnetic fields are quantum phase transitions and the transitions are governed by percolation effects—quantum mechanical in the former and classical in the latter cases. Compared to the hole-doped cuprates, the SITs in the electron-doped system occur at critical sheet resistances (Rc) much lower than the pair quantum resistance RQ=h /(2e ) 2=6.45 k Ω , suggesting the possible existence of fermionic excitations at finite temperatures at the insulating phase near the SITs.

  16. Strong coupling critique of spin fluctuation driven charge order in underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Mishra, Vivek; Norman, M. R.

    2015-08-01

    Charge order has emerged as a generic feature of doped cuprates, leading to important questions about its origin and its relation to superconductivity. Recent experiments on two classes of hole doped cuprates indicate a novel d -wave symmetry for the order. These were motivated by earlier spin fluctuation theoretical studies based on an expansion about hot spots in the Brillouin zone that indicated such an order would be competitive with d -wave superconductivity. Here, we reexamine this problem by solving strong coupling equations in the full Brillouin zone for experimentally relevant parameters. We find that bond-oriented order, as seen experimentally, is strongly suppressed. We also include coupling to B1 g phonons and do not see any qualitative change. Our results argue against an itinerant model for the charge order, implying instead that such order is likely due to Coulombic phase separation of the doped holes.

  17. Wiedemann-Franz law in the underdoped cuprate superconductor YBa2Cu3Oy

    NASA Astrophysics Data System (ADS)

    Grissonnanche, G.; Laliberté, F.; Dufour-Beauséjour, S.; Matusiak, M.; Badoux, S.; Tafti, F. F.; Michon, B.; Riopel, A.; Cyr-Choinière, O.; Baglo, J. C.; Ramshaw, B. J.; Liang, R.; Bonn, D. A.; Hardy, W. N.; Krämer, S.; LeBoeuf, D.; Graf, D.; Doiron-Leyraud, N.; Taillefer, Louis

    2016-02-01

    The electrical and thermal Hall conductivities of the cuprate superconductor YBa2Cu3Oy , σx y and κx y, were measured in a magnetic field up to 35 T, at a hole concentration (doping) p =0.11 . In the T =0 limit, we find that the Wiedemann-Franz law, κx y/T =(π2/3 ) (kB/e ) 2σx y , is satisfied for fields immediately above the vortex-melting field Hvs. This rules out the existence of a vortex liquid at T =0 and it puts a clear constraint on the nature of the normal state in underdoped cuprates, in a region of the doping phase diagram where charge-density-wave order is known to exist. As the temperature is raised, the Lorenz ratio, Lxy=κxy/(σxyT ) , decreases rapidly, indicating that strong small-q scattering processes are involved.

  18. TOPICAL REVIEW: Theory of extrinsic and intrinsic tunnelling in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Beanland, J.; Alexandrov, A. S.

    2010-10-01

    There has been a huge theoretical and experimental push to try to illuminate the mechanism behind the high-temperature superconductivity of copper oxides. Cuprates are distinguishable from conventional metallic superconductors in originating from the doping of the parent charge-transfer insulators. The superconducting parts are weakly coupled two-dimensional doped layers held together by the parent lattice. Apart from their high-Tc they have other characteristic features including the 'superconducting' gap (SG) which develops below the superconducting critical temperature and can be seen in extrinsic and intrinsic tunnelling experiments as well as using high-resolution angle-resolved photoemission (ARPES); there also exists another energy gap, the 'pseudogap' (PG), which is a large anomalous gap that exists well above Tc. We present a brief review of recent theories behind the pseudogap and discuss in detail one specific (polaronic) approach which explains the SG, PG and unusual tunnelling characteristics of cuprate superconductors.

  19. Perspective on the phase diagram of cuprate high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Rybicki, Damian; Jurkutat, Michael; Reichardt, Steven; Kapusta, Czesław; Haase, Jürgen

    2016-05-01

    Universal scaling laws can guide the understanding of new phenomena, and for cuprate high-temperature superconductivity the influential Uemura relation showed, early on, that the maximum critical temperature of superconductivity correlates with the density of the superfluid measured at low temperatures. Here we show that the charge content of the bonding orbitals of copper and oxygen in the ubiquitous CuO2 plane, measured with nuclear magnetic resonance, reproduces this scaling. The charge transfer of the nominal copper hole to planar oxygen sets the maximum critical temperature. A three-dimensional phase diagram in terms of the charge content at copper as well as oxygen is introduced, which has the different cuprate families sorted with respect to their maximum critical temperature. We suggest that the critical temperature could be raised substantially if one were able to synthesize materials that lead to an increased planar oxygen hole content at the expense of that of planar copper.

  20. Electronic structure of cuprate superconductors in a full charge-spin recombination scheme

    NASA Astrophysics Data System (ADS)

    Feng, Shiping; Kuang, Lülin; Zhao, Huaisong

    2015-10-01

    A long-standing unsolved problem is how a microscopic theory of superconductivity in cuprate superconductors based on the charge-spin separation can produce a large electron Fermi surface. Within the framework of the kinetic-energy driven superconducting mechanism, a full charge-spin recombination scheme is developed to fully recombine a charge carrier and a localized spin into a electron, and then is employed to study the electronic structure of cuprate superconductors in the superconducting-state. In particular, it is shown that the underlying electron Fermi surface fulfills Luttinger's theorem, while the superconducting coherence of the low-energy quasiparticle excitations is qualitatively described by the standard d-wave Bardeen-Cooper-Schrieffer formalism. The theory also shows that the observed peak-dip-hump structure in the electron spectrum and Fermi arc behavior in the underdoped regime are mainly caused by the strong energy and momentum dependence of the electron self-energy.

  1. Collective nature of spin excitations in superconducting cuprates probed by resonant inelastic X-ray scattering.

    PubMed

    Minola, M; Dellea, G; Gretarsson, H; Peng, Y Y; Lu, Y; Porras, J; Loew, T; Yakhou, F; Brookes, N B; Huang, Y B; Pelliciari, J; Schmitt, T; Ghiringhelli, G; Keimer, B; Braicovich, L; Le Tacon, M

    2015-05-29

    We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa_{2}Cu_{3}O_{6+x} over a wide range of doping levels (0.1≤x≤1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from incoherent particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed. PMID:26066453

  2. Nematicity in stripe ordered cuprates probed via resonant x-ray scattering

    DOE PAGESBeta

    Achkar, A. J.; Zwiebler, M.; McMahon, Christopher; He, F.; Sutarto, R.; Dijianto, Isaiah; Hao, Zhihao; Gingras, Michael J.P.; Hucker, M.; Gu, G. D.; et al

    2016-02-05

    We found that in underdoped cuprate superconductors, a rich competition occurs between superconductivity and charge density wave (CDW) order. Whether rotational symmetry-breaking (nematicity) occurs intrinsically and generically or as a consequence of other orders is under debate. Here, we employ resonant x-ray scattering in stripe-ordered superconductors (La,M)2CuO4 to probe the relationship between electronic nematicity of the Cu 3d orbitals, structure of the (La,M)2O2 layers, and CDW order. We find distinct temperature dependences for the structure of the (La,M)2O2 layers and the electronic nematicity of the CuO2 planes, with only the latter being enhanced by the onset of CDW order. Ourmore » results identify electronic nematicity as an order parameter that is distinct from a purely structural order parameter in underdoped striped cuprates.« less

  3. Present status of the theory of the high-Tc cuprates

    NASA Astrophysics Data System (ADS)

    Anderson, P. W.

    2006-04-01

    The Gutzwiller-projected mean-field theory, also called plain vanilla or renormalized mean-field theory, is explained, and its successes and possible extensions in describing the phenomenology of the cuprate superconductors are discussed. Throughout, we emphasize that while this is a Hartree-Fock-based BCS theory, it embodies fundamental differences from conventional perturbative many-body theory which may be characterized by calling it a theory of the doped Mott insulator.

  4. Material and Doping Dependence of the Nodal and Antinodal Dispersion Renormalizations in Single- and Multilayer Cuprates

    DOE PAGESBeta

    Johnston, S.; Lee, W. S.; Chen, Y.; Nowadnick, E. A.; Moritz, B.; Shen, Z. -X.; Devereaux, T. P.

    2010-01-01

    We presenmore » t a review of bosonic renormalization effects on electronic carriers observed from angle-resolved photoemission spectra in the cuprates. Specifically, we discuss the viewpoint that these renormalizations represent coupling of the electrons to the lattice and review how materials dependence, such as the number of Cu O 2 layers, and doping dependence can be understood straightforwardly in terms of several aspects of electron-phonon coupling in layered correlated materials.« less

  5. Interplay of pair density wave and charge density wave order in the cuprate pseudogap phase

    NASA Astrophysics Data System (ADS)

    Agterberg, Daniel; Amin, Adil

    Recent x-ray measurements in the cuprate YBCO suggest that the charge density wave (CDW) order seen at high-field has a different c-axis structure than that seen at zero-field and further suggests that CDW order breaks the c-axis mirror plane symmetry of the CuO2 layers. We examine pair density wave order that induces CDW order consistent with these observations.

  6. Novel magnetic excitations in a model cuprate high-Tc superconductor

    NASA Astrophysics Data System (ADS)

    Li, Yuan

    2011-03-01

    Magnetic fluctuations might be essential to the mechanism of high-temperature superconductivity in the cuprates. For a long time, such fluctuations have been theoretically regarded as arising from the antiferromagnetic correlations within the copper-oxygen layers, and experimental studies of magnetic excitation spectrum have mainly been carried out near the corresponding wave vector (1/2,~1/2). Following neutron diffraction experiments which demonstrated the universal existence of a `` q ~=~0 antiferromagnetic order'' in the pseudogap phase of three different cuprates [1-3], our recent inelastic neutron scattering experiments on the model compound HgBa 2 Cu O4 + δ (Hg1201) revealed the existence of unusual magnetic excitations that weakly disperse throughout the entire Brillouin zone [4,5]. Like the q ~=~0 antiferromagnetic order, the new excitations are observed in the pseudogap phase and therefore appear to be associated with the order. The excitations possess very large spectral weights at well-defined characteristic energies that are comparable to the resonance energy and to those of electron-boson-coupling features observed in a wide range of cuprates, highlighting their possible influence on the electronic structure. These findings demonstrate that the pseudogap state is a distinct phase of matter rather than a mere crossover. They furthermore cast doubt on the presumed predominant importance of the wave vector (1/2,~1/2) in the magnetic excitation spectrum, and have the profound implication that a single-band description of the cuprates is insufficient. Project was funded by DOE and NSF grants. The author achnowledges the Alexander von Humboldt Foundation.

  7. On the Interpretation of the Nernst Effect Measurements in the Cuprates

    NASA Astrophysics Data System (ADS)

    Ussishkin, Iddo; Sondhi, S. L.

    We consider the large Nernst signal discovered by Ong and collaborators in hole-doped cuprates, in particular in the pseudogap regime. Based on our previous quantitative calculations together with Huse [Phys. Rev. Lett. 89, 287001 (2002)], we discuss the interpretation of the experimental observations as arising from superconducting fluctuations and its relation to the vortex scenario proposed by Ong. We also comment on the implications of the Nernst analysis for understanding the full range of pseudogap phenomena.

  8. Inverse correlation between quasiparticle mass and T c in a cuprate high-T c superconductor.

    PubMed

    Putzke, Carsten; Malone, Liam; Badoux, Sven; Vignolle, Baptiste; Vignolles, David; Tabis, Wojciech; Walmsley, Philip; Bird, Matthew; Hussey, Nigel E; Proust, Cyril; Carrington, Antony

    2016-03-01

    Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature T c is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-T c superconductivity. We have tested the robustness of this correlation between m* and T c by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as T c increases under pressure. This inverse correlation between m* and T c suggests that quantum fluctuations of the charge order enhance m* but do not enhance T c. PMID:27034989

  9. TOPICAL REVIEW: The physics behind high-temperature superconducting cuprates: the 'plain vanilla' version of RVB

    NASA Astrophysics Data System (ADS)

    Anderson, P. W.; Lee, P. A.; Randeria, M.; Rice, T. M.; Trivedi, N.; Zhang, F. C.

    2004-06-01

    One of the first theoretical proposals for understanding high-temperature superconductivity in the cuprates was Anderson's RVB theory using a Gutzwiller projected BCS wavefunction as an approximate ground state. Recent work by Paramekanti et al has shown that this variational approach gives a semi-quantitative understanding of the doping dependences of a variety of experimental observables in the superconducting state of the cuprates. In this paper we revisit these issues using the 'renormalized mean field theory' of Zhang et al based on the Gutzwiller approximation in which the kinetic and superexchange energies are renormalized by different doping-dependent factors gt and gS respectively. We point out a number of consequences of this early mean field theory for experimental measurements which were not available when it was first explored, and observe that it is able to explain the existence of the pseudogap, properties of nodal quasiparticles and approximate spin-charge separation, the latter leading to large renormalizations of the Drude weight and superfluid density. We use the Lee-Wen theory of the phase transition as caused by thermal excitation of nodal quasiparticles, and also obtain a number of further experimental confirmations. Finally, we remark that superexchange, and not phonons, is responsible for d-wave superconductivity in the cuprates.

  10. Universality of commensurate 4 a-period charge density modulations throughout the cuprate pseudogap regime

    NASA Astrophysics Data System (ADS)

    Mesaros, Andrej; Fujita, Kazuhiro; Hamidian, Mohammad; Eisaki, Hiroshi; Uchida, Shin-Ichi; Davis, J. C.; Lawler, Michael J.; Kim, Eun-Ah

    Theories for the hole-doped Mott insulator, representing underdoped cuprates, are based upon the strong real space (r-space) interactions, and have long predicted a modulation of charge that is commensurate with the underlying lattice. Such a charge density modulation (CDM) state is unrelated to any momentum space (k-space) features such as the nesting of regions on a Fermi surface. Experimentally, with increasing hole density, the reported wavevector Q of the CDM diminishes continuously with increasing hole-density as if driven by k-space phenomena. Using a novel technique based upon phase-sensitive electronic structure visualization, we demonstrate that the cuprate CDM actually exhibits a commensurate 4 a-period throughout the entire underdoped region of the Bi2 Sr2 CaCu2O8 phase diagram. Our technique is designed for extracting Q from inhomogeneous, short-ranged CDM, as the ones observed in experiments. Thus, a strong-interaction r-space perspective appears to be relevant to achieving a predictive theory for the cuprate pseudogap regime.

  11. Progress in Neutron Scattering Studies of Spin Excitations in High-T(c) Cuprates

    SciTech Connect

    Fujita M.; Tranquada J.; Hiraka, H.; Matsuda, M.; Matsuura, M.; Wakimoto, S.; Xu, G.; Yamada, K.

    2012-01-01

    Neutron scattering experiments continue to improve our knowledge of spin fluctuations in layered cuprates, excitations that are symptomatic of the electronic correlations underlying high-temperature superconductivity. Time-of-flight spectrometers, together with new and varied single crystal samples, have provided a more complete characterization of the magnetic energy spectrum and its variation with carrier concentration. While the spin excitations appear anomalous in comparison with simple model systems, there is clear consistency among a variety of cuprate families. Focusing initially on hole-doped systems, we review the nature of the magnetic spectrum, and variations in magnetic spectral weight with doping. We consider connections with the phenomena of charge and spin stripe order, and the potential generality of such correlations as suggested by studies of magnetic-field and impurity induced order. We contrast the behavior of the hole-doped systems with the trends found in the electron-doped superconductors. Returning to hole-doped cuprates, studies of translation-symmetry-preserving magnetic order are discussed, along with efforts to explore new systems. We conclude with a discussion of future challenges.

  12. Itinerant effects and enhanced magnetic interactions in Bi-based multilayer cuprates

    DOE PAGESBeta

    Dean, M. P. M.; James, A. J. A.; Walters, A. C.; Bisogni, V.; Jarrige, I.; Hücker, M.; Giannini, E.; Fujita, M.; Pelliciari, J.; Huang, Y. B.; et al

    2014-12-04

    The cuprate high temperature superconductors exhibit a pronounced trend in which the superconducting transition temperature, T c, increases with the number of CuO₂ planes, n, in the crystal structure. We compare the magnetic excitation spectrum of Bi₂₊xSr₂₋xCuO₆+δ (Bi-2201) and Bi₂Sr₂Ca₂Cu₃O₁₀₊δ (Bi-2223), with n = 1 and n = 3 respectively, using Cu L₃-edge resonant inelastic x-ray scattering (RIXS). Near the anti-nodal zone boundary we find the paramagnon energy in Bi-2223 is substantially higher than that in Bi-2201, indicating that multilayer cuprates host stronger effective magnetic exchange interactions, providing a possible explanation for the Tc vs. n scaling. In contrast, themore » nodal direction exhibits very strongly damped, almost non-dispersive excitations. As a result, we argue that this implies that the magnetism in the doped cuprates is partially itinerant in nature.« less

  13. Power-law optical conductivity from unparticles: Application to the cuprates

    NASA Astrophysics Data System (ADS)

    Limtragool, Kridsanaphong; Phillips, Philip

    2015-10-01

    We calculate the optical conductivity by using several models for unparticle or scale-invariant matter. Within a Gaussian action for unparticles that is gauged with Wilson lines, we find that the conductivity computed from the Kubo formalism with vertex corrections yields no nontrivial deviation from the free-theory result. This result obtains because, at the Gaussian level, unparticles are just a superposition of particle fields and hence any transport property must be consistent with free theory. Beyond the Gaussian approach, we adopt the continuous-mass formulation of unparticles and calculate the Drude conductivity directly. We show that unparticles in this context can be tailored to yield an algebraic conductivity that scales as ω-2 /3 with the associated phase angle between the imaginary and real parts of arctanσ/2σ1=60∘ , as is seen in the cuprates. Given the recent results [J. High Energy Phys. 4, 40 (2014), 10.1007/JHEP04(2014)040; J. High Energy Phys. 7, 24 (2015), 10.1007/JHEP07(2015)024; arXiv:1506.06769] that gravitational crystals lack a power-law optical conductivity, this constitutes the first consistent account of the ω-2 /3 conductivity and the phase angle seen in optimally doped cuprates. Our results indicate that, at each frequency in the scaling regime, excitations on all energy scales contribute. Hence, incoherence is at the heart of the power law in the optical conductivity in strongly correlated systems such as the cuprates.

  14. Crystal structure of the thermochromic bis-(di-ethyl-ammonium) tetra-chlorido-cuprate(II) complex.

    PubMed

    Aldrich, Emily P; Bussey, Katherine A; Connell, Jennifer R; Reinhart, Erin F; Oshin, Kayode D; Mercado, Brandon Q; Oliver, Allen G

    2016-01-01

    In the structure of the title complex salt, (Et2NH2)2[CuCl4], the asymmetric unit consists of four unique di-ethyl-ammonium cations and three unique tetra-chlorido-cuprate anions. Two of the three anions are located with their copper atoms on independent crystallographic twofold axes, while the remaining tetra-chlorido-cuprate is located at a general position of the ortho-rhom-bic space group P21212. Two of the three Cu atoms adopt a distorted square-planar/disphenoidal geometry and the third Cu atom has a regular square-planar coordination environment. The di-ethyl-ammonium cations form an extensive hydrogen-bonded network through N-H⋯Cl inter-actions with the tetra-chlorido-cuprate anions, resulting in a two-dimensional sheet-like hydrogen-bonded network parallel to the ab direction. The complex was observed to undergo a color shift from deep green at room temperature to pale yellow at temperatures above 328 K. PMID:26870581

  15. Probing broken symmetry states in cuprate superconductors with polarization-sensitive infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Mukherjee, Alok; Arik, Mumtaz Murat; Seo, Jungryeol; Cerne, John; Zhang, Hao; Xu, Ke Jun; Wei, John Y. T.; Armitage, N. P.; Kirzhner, T.; Koren, G.

    The nature of the pseudogap state in high-temperature superconducting (HTS) cuprates has drawn a lot of attention in the past two decades. A fundamental question is whether the pseudogap is a distinct phase with its own broken symmetries. Recent optical studies in the near-IR (800 meV) and THz (2-6 meV) ranges have observed symmetry breaking in the pseudogap state of HTS cuprates, suggesting that the pseudogap is a distinct phase. To probe the spectral character of this broken symmetry, we have performed infrared/visible Faraday and Kerr effect measurements at zero magnetic field and various temperatures on a series of HTS cuprate thin films, grown epitaxially by pulsed laser-ablated deposition. We will present and discuss our data, primarily complex Faraday/Kerr angle as a function of energy (0.1-3 eV), temperature (10-300K) and sample orientation with respect to the incident light polarization. This work supported by NSF-DMR1410599, NSERC, CFI-OIT and the Canadian Institute for Advanced Research.

  16. Direct phase-sensitive identification of a d-form factor density wave in underdoped cuprates

    PubMed Central

    Fujita, Kazuhiro; Hamidian, Mohammad H.; Edkins, Stephen D.; Kim, Chung Koo; Kohsaka, Yuhki; Azuma, Masaki; Takano, Mikio; Takagi, Hidenori; Eisaki, Hiroshi; Uchida, Shin-ichi; Allais, Andrea; Lawler, Michael J.; Kim, Eun-Ah; Sachdev, Subir; Davis, J. C. Séamus

    2014-01-01

    The identity of the fundamental broken symmetry (if any) in the underdoped cuprates is unresolved. However, evidence has been accumulating that this state may be an unconventional density wave. Here we carry out site-specific measurements within each CuO2 unit cell, segregating the results into three separate electronic structure images containing only the Cu sites [Cu(r)] and only the x/y axis O sites [Ox(r) and Oy(r)]. Phase-resolved Fourier analysis reveals directly that the modulations in the Ox(r) and Oy(r) sublattice images consistently exhibit a relative phase of π. We confirm this discovery on two highly distinct cuprate compounds, ruling out tunnel matrix-element and materials-specific systematics. These observations demonstrate by direct sublattice phase-resolved visualization that the density wave found in underdoped cuprates consists of modulations of the intraunit-cell states that exhibit a predominantly d-symmetry form factor. PMID:24989503

  17. Relationship between critical temperature and core orbital coupling in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Zhao, Bo; Chen, Ning

    2016-04-01

    Because superconductivity and several relevant phenomena of high-temperature superconductors (HTSCs) arise from interactions of valence electrons near the Fermi surface, the valence orbital coupling has usually been thought to be critical to understanding the electronic pairing mechanism which seems work without the core coupling orbitals. But, as strong electronic correlations are believed to be essential for a comprehensive understanding of the cuprate superconductors, the Fermi surface is influenced directly or indirectly by all orbital couplings in the entire energy band. In this paper, we focused on the core orbital coupling which arises from the overlap between the Oxygen's 2 s core orbital and the core p orbital of neighboring ion of CuO2 layers as they have a similar energy level ranging from -12 ∼ -23 eV below the Fermi level. The characters of this core coupling are varied with different kinds of neighboring ions or from the crystal structures. Based on the experimental superconducting critical temperature (Tc) data, we found that the binding energy differences between the valence couplings and the core couplings are positively related with the systemic Tc values for all cuprate superconductors. Obviously, this relationship suggests that the electron pairing nature of superconductivity for all cuprates might arise from the sp core orbital coupling.

  18. Underlying mechanisms of pseudogap phenomena and Bose-liquid superconductivity in high-Tc cuprates

    NASA Astrophysics Data System (ADS)

    Dzhumanov, S.; Karimboev, E. X.; Djumanov, Sh. S.

    2016-06-01

    We show that the high-Tc cuprates are non-BCS superconductors exhibiting distinct pseudogap (PG) behaviors (related to real and momentum space excitations) and other anomalies above Tc, novel Bose-liquid superconductivity below Tc, and also a λ-like superconducting (SC) transition at Tc similar to the λ transition in liquid 4He. In these materials, the relevant charge carriers are polarons which are bound into bosonic Cooper pairs above Tc followed by condensing into a Bose superfluid at Tc. We found that the polaronic effects and related PG weaken with increasing of the doping level and disappear in the overdoped region, where the crossover from Bose-liquid to Fermi-liquid (BCS-type) superconductivity occurs at the quantum critical point. We identify the real phase diagrams of the cuprates, the PG and vortex-like states above Tc, the novel SC state and two distinct SC phases below Tc like two superfluid phases of 3He, and explain the rich cuprate phenomenology from lightly doped to overdoped region.

  19. Inverse correlation between quasiparticle mass and Tc in a cuprate high-Tc superconductor

    PubMed Central

    Putzke, Carsten; Malone, Liam; Badoux, Sven; Vignolle, Baptiste; Vignolles, David; Tabis, Wojciech; Walmsley, Philip; Bird, Matthew; Hussey, Nigel E.; Proust, Cyril; Carrington, Antony

    2016-01-01

    Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature Tc is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-Tc superconductivity. We have tested the robustness of this correlation between m* and Tc by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as Tc increases under pressure. This inverse correlation between m* and Tc suggests that quantum fluctuations of the charge order enhance m* but do not enhance Tc. PMID:27034989

  20. 2011 Aspen Winter Conference on Contrasting Superconductivity of Pnictides and Cuprates

    SciTech Connect

    Johnson, P.; Schmalian, J.; Canfield, P.; Chakravarty, S.

    2011-05-02

    Our quest for materials with better properties is closely integral to the fabric of our society. Currently the development of materials that will allow for improved generation, transport, and storage of energy is at the forefront of our research in condensed matter physics and materials science. Among these materials, compounds that exhibit correlated electron states and emergent phenomena such as superconductivity have great promise, but also difficulties that need to be overcome: problems associated with our need to reliably find, understand, improve and control these promising materials. At the same time, the field of correlated electrons represents the frontier of our understanding of the electronic properties of solids. It contains deep open scientific issues within the broad area of quantum phenomena in matter. The aim of this workshop is to explore and understand the physics of recently discovered Fe-based high-temperature superconductors and contrast and compare them with the cuprates. The superconductivity in iron pnictides, with transition temperatures in excess of 55 K, was discovered in early 2008. The impact of this discovery is comparable to cuprates discovered in 1986. At the same time a number of recent experimental developments in cuprates may lead to a shift in our thinking with regards to these materials. There is therefore much to be learned by devoting a conference in which both classes of superconductors are discussed, especially at this nascent stage of the pnictides.

  1. Interpretation of Scanning Tunneling Quasiparticle Interference and Impurity States in Cuprates

    SciTech Connect

    Kreisel, A.; Choubey, P.; Berlijn, T.; Ku, W.; Andersen, B. M.; Hirschfeld, P. J.

    2015-05-27

    We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi2Sr2CaCu2O8 can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude “filter” theories on a microscopic foundation and solves a long standing puzzle. We then study quasiparticle interference (QPI) phenomena induced by out-of-plane weak potential scatterers, and show how patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging.

  2. Interpretation of scanning tunneling quasiparticle interference and impurity states in cuprates

    SciTech Connect

    Kreisel, Andreas; Choubey, Peayush; Berlijn, Tom; Ku, W.; Andersen, Brian M.; Hirschfeld, Peter J.

    2015-05-27

    We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov–de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi2Sr2CaCu2O8 can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude “filter” theories on a microscopic foundation and solves a long-standing puzzle. We then study quasiparticle interference phenomena induced by out-of-plane weak potential scatterers, and show how patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Furthermore, our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging.

  3. Interpretation of Scanning Tunneling Quasiparticle Interference and Impurity States in Cuprates

    DOE PAGESBeta

    Kreisel, A.; Choubey, P.; Berlijn, T.; Ku, W.; Andersen, B. M.; Hirschfeld, P. J.

    2015-05-27

    We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi2Sr2CaCu2O8 can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude “filter” theories on a microscopic foundation and solves a long standing puzzle. We then study quasiparticle interference (QPI) phenomena induced by out-of-plane weak potential scatterers, andmore » show how patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging.« less

  4. Interpretation of scanning tunneling quasiparticle interference and impurity states in cuprates

    DOE PAGESBeta

    Kreisel, Andreas; Choubey, Peayush; Berlijn, Tom; Ku, W.; Andersen, Brian M.; Hirschfeld, Peter J.

    2015-05-27

    We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov–de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi2Sr2CaCu2O8 can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude “filter” theories on a microscopic foundation and solves a long-standing puzzle. We then study quasiparticle interference phenomena induced by out-of-plane weak potential scatterers, and show howmore » patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Furthermore, our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging.« less

  5. Effective single-band models for the high-Tc cuprates. II. Role of apical oxygen

    NASA Astrophysics Data System (ADS)

    Raimondi, R.; Jefferson, J. H.; Feiner, L. F.

    1996-04-01

    An effective single-band model for the cuprates is derived by a cell-perturbation method from a five-band model which includes d3z2-r2 orbitals on copper and pz orbitals on apical oxygen. In addition to the usual Zhang-Rice singlets of A1 symmetry, there are two-hole cell states of B1 symmetry, which can become low in energy and depend sensitively on the apical oxygen ions. Provided that hybridization with the apical oxygen orbital is sufficiently weak to permit reduction to a t-t'-J model, the main effect of the B1-symmetry states is to renormalize the effective next-nearest-neighbor hopping (t') of doped holes. This effect can be quite large and may even change the sign of t'. The variation of t' between various compounds due to differences in crystal structure is shown to correlate with Tmaxc, the critical temperature at optimum doping, suggesting that t' may be a crucial parameter for the low-energy physics, which moreover differentiates between the various cuprates. The effective single-band model is shown to break down when the apex level approaches the in-plane oxygen level, and to describe that situation, which cannot be ruled out completely for the cuprates with present experimental evidence, we propose a specific minimal effective (two-band) model.

  6. Pseudogap phase in cuprates: Oxygen orbital moments instead of circulating currents

    NASA Astrophysics Data System (ADS)

    Moskvin, A. S.

    2012-11-01

    Circulating current loops within the cuprate unit cell are proposed to play a key role in the physics of the pseudogap phase. However, main experimental observations motivated by this sophisticated proposal and seemingly supporting the circulating current model can be explained within a simple and physically clear microscopic model. It has been argued that, instead of a well-isolated Zhang-Rice (ZR) singlet 1 A 1 g , the ground state of the hole center [CuO4]5- (cluster analog of Cu3+ ion) in cuprates should be described by a complex 1 A 1 g -1,3 B 2 g -1,3 E u multiplet, formed by a competition of conventional hybrid Cu 3 d-O 2 p b_{1g} (σ ) ∝ d_{x^2 - y^2 } state and purely oxygen nonbonding O 2 pπ states with a 2 g (π) and e ux, y (π) symmetry. In contrast to inactive ZR singlet we arrive at several novel competing orbital and spin-orbital order parameters, e.g., Ising-like net orbital magnetic moment, orbital toroidal moment, intra-plaquette's staggered order of Ising-like oxygen orbital magnetic moments. As a most impressive validation of the non-ZR model we explain fascinating results of recent neutron scattering measurements that revealed novel type of magnetic ordering in pseudogap phase of several hole-doped cuprates.

  7. Earth Resources

    ERIC Educational Resources Information Center

    Brewer, Tom

    1970-01-01

    Reviews some of the more concerted, large-scale efforts in the earth resources areas" in order to help the computer community obtain insights into the activities it can jointly particpate in withthe earth resources community." (Author)

  8. Phase fluctuation in overdoped cuprates? Superconducting dome due to Mott-ness of the tightly bound preformed pairs

    NASA Astrophysics Data System (ADS)

    Ku, Wei; Yang, Fan

    2015-03-01

    In contrast to the current lore, we demonstrate that even the overdoped cuprates suffer from superconducting phase fluctuation in the strong binding limit. Specifically, the Mott-ness of the underlying doped holes dictates naturally a generic optimal doping around 15% and nearly complete loss of phase coherence around 25%, giving rise to a dome shape of superconducting transition temperature in excellent agreement with experimental observations of the cuprates. We verify this effect with a simple estimation using Gutzwiller approximation of the preformed pairs, obtained through variational Monte Carlo calculation. This realization suggests strongly the interesting possibility that the high-temperature superconductivity in the cuprates might be mostly described by Bose-Einstein condensation, without crossing over to amplitude fluctuating Cooper pairs. Supported by Department of Energy, Office of Basic Energy Science DE-AC02-98CH10886.

  9. Recent high-magnetic-field experiments on the 'high Tc' cuprates: Fermi-surface instabilities as a driver for superconductivity

    SciTech Connect

    Singleton, John; Mc Donald, Ross D; Cox, Susan

    2008-01-01

    The authors give a brief review of high-magnetic-field quantum-oscillation measurements on cuprate superconductors. In the case of the underdoped cuprates, a number of small Fermi-surface pockets are observed, probably due to the incommensurate nesting of the predicted (large) hole Fermi surface. The Fermi-surface instabilities that drive this nesting are also likely to result in the incommensurate spin fluctuations observed in inelastic neutron-scattering measurements. They suggest that the unusually high superconducting transitions in the cuprates are driven by an exact mapping of these incommensurate spin fluctuations onto the d{sub x{sup 2}-y{sup 2}} Cooper-pair wavefunction. The maximum energy of the fluctuations {approx} 100s of Kelvin gives an appropriate energy scale for the superconducting transition temperature.

  10. Electric Charge Transfer and Scattering of Its Carriers in Cuprates of the 1-2-3 System

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Khadzhai, G. Ya.; Dobrovolskiy, O. V.; Kamchatnaya, S. N.; Nazyrov, Z. F.

    2016-04-01

    We show that the temperature dependences of the basal-plane electrical resistance in cuprates of the 1-2-3 system can be described as a consequence of scattering of charge carriers on phonons and defects in conjunction with the fluctuation conductivity. The electron-phonon parameters values deduced from fitting the experimental data to recognized models are close to those for metallic alloys of complex composition. It is revealed that at a large oxygen deficit (low superconducting transition temperatures T_c), the superconducting behavior of the studied cuprates has similarities with that of complex superconducting alloys. At the optimum oxygen deficit (maximal T_cs), superconductivity in the investigated cuprates is likely governed by some other mechanisms.

  11. Discover Earth

    NASA Technical Reports Server (NTRS)

    Steele, Colleen

    1998-01-01

    Discover Earth is a NASA-sponsored project for teachers of grades 5-12, designed to: (1) enhance understanding of the Earth as an integrated system; (2) enhance the interdisciplinary approach to science instruction; and (3) provide classroom materials that focus on those goals. Discover Earth is conducted by the Institute for Global Environmental Strategies in collaboration with Dr. Eric Barron, Director, Earth System Science Center, The Pennsylvania State University; and Dr. Robert Hudson, Chair, the Department of Meteorology, University of Maryland at College Park. The enclosed materials: (1) represent only part of the Discover Earth materials; (2) were developed by classroom teachers who are participating in the Discover Earth project; (3) utilize an investigative approach and on-line data; and (4) can be effectively adjusted to classrooms with greater/without technology access. The Discover Earth classroom materials focus on the Earth system and key issues of global climate change including topics such as the greenhouse effect, clouds and Earth's radiation balance, surface hydrology and land cover, and volcanoes and climate change. All the materials developed to date are available on line at (http://www.strategies.org) You are encouraged to submit comments and recommendations about these materials to the Discover Earth project manager, contact information is listed below. You are welcome to duplicate all these materials.

  12. Emery vs. Hubbard model for cuprate superconductors: a composite operator method study

    NASA Astrophysics Data System (ADS)

    Avella, Adolfo; Mancini, Ferdinando; Mancini, Francesco Paolo; Plekhanov, Evgeny

    2013-06-01

    Within the composite operator method (COM), we report the solution of the Emery model (also known as p- d or three band model), which is relevant for the cuprate high- T c superconductors. We also discuss the relevance of the often-neglected direct oxygen-oxygen hopping for a more accurate, sometimes unique, description of this class of materials. The benchmark of the solution is performed by comparing our results with the available quantum Monte Carlo ones. Both single-particle and thermodynamic properties of the model are studied in detail. Our solution features a metal-insulator transition at half filling. The resulting metal-insulator phase diagram agrees qualitatively very well with the one obtained within dynamical mean-field theory. We discuss the type of transition (Mott-Hubbard (MH) or charge-transfer (CT)) for the microscopic (ab initio) parameter range relevant for cuprates getting, as expected a CT type. The emerging single-particle scenario clearly suggests a very close relation between the relevant sub-bands of the three- (Emery) and the single-band (Hubbard) models, thus providing an independent and non-perturbative proof of the validity of the mapping between the two models for the model parameters optimal to describe cuprates. Such a result confirms the emergence of the Zhang-Rice scenario, which has been recently questioned. We also report the behavior of the specific heat and of the entropy as functions of the temperature on varying the model parameters as these quantities, more than any other, depend on and, consequently, reveal the most relevant energy scales of the system.

  13. Intra unit cell electronic structure of the d-symmetry form factor density wave in the underdoped cuprates - Part II

    NASA Astrophysics Data System (ADS)

    Edkins, Stephen; Fujita, Kazuhiro; Hamidian, Mohammad; Kim, Chung Koo; MacKenzie, Andrew; Eisaki, Hiroshi; Uchida, Shinichi; Lawler, Michael; Kim, Eun-Ah; Sachdev, Subir; Davis, Seamus

    2015-03-01

    A central issue of cuprate superconductivity research is to understand the nature of the unknown phase called the pseudogap and its relationship to the d-wave superconductivity. To approach this we use spectroscopic imaging STM to study the electronic structure of Bi2Sr2CaCu2O8+δ. Using our recently developed technique of sub-lattice phase-resolved electronic structure visualization within each CuO2 unit-cell, we discovered a d-symmetry form factor density wave within the cuprate pseudogap state. In this talk, part II, we report on the electronic structure of the density wave and its interplay with superconductivity.

  14. Synthesis of a new layered cuprate, Gd 2CaBa 2Ti 2Cu 2O 12

    NASA Astrophysics Data System (ADS)

    Fukuoka, A.; Adachi, S.; Sugano, T.; Wu, X.-J.; Yamauchi, H.

    1994-10-01

    A new layered cuprate, Gd 2CaBa 2Ti 2Cu 2O 12, which has a perovskite-related structure, has been discovered. The crystal structure is investigated by powder X-ray diffraction, electron diffraction and Rietveld analysis. It has a tetragonal symmetry with lattice parameters a=3.894 Å and c=35.49 Å. In the crystal there are sheets consisting of CuO 5 pyramids, which is one of the common features of p-type high- Tc superconducting cuprates.

  15. Role of Strong Correlation in the Recent Angle-Resolved Photoemission Spectroscopy Experiments on Cuprate Superconductors

    SciTech Connect

    Yunoki, S.; Dagotto, Elbio R; Sorella, S.

    2005-01-01

    Motivated by recent photoemission experiments on cuprates, the low-lying excitations of a strongly correlated superconducting state are studied numerically. It is observed that along the nodal direction these low-lying one-particle excitations show a linear momentum dependence for a wide range of excitation energies and, thus, they do not present a kinklike structure. The nodal Fermi velocity vF, as well as other observables, are systematically evaluated directly from the calculated dispersions, and they are found to compare well with experiments. It is argued that the parameter dependence of v{sub F} is quantitatively explained by a simple picture of a renormalized Fermi velocity.

  16. Possibility of c-axis voltage steps for a cuprate superconductor in a resonant cavity

    NASA Astrophysics Data System (ADS)

    Tornes, I.; Stroud, D.

    2003-08-01

    Very anisotropic cuprate superconductors, such as BiSr2Ca2CuO8+x, when driven by currents parallel to the c axis, behave like stacks of underdamped Josephson junctions. Here, we analyze the possibility that such a stack can be caused to phase lock, to exhibit self-induced resonant voltage steps (SIRS’s), and hence to radiate coherently when placed in a suitable resonant electromagnetic cavity. We analyze this possibility using equations of motion developed to describe such SIRS’s in stacks of artificial Josephson junctions. We conclude that such steps might be observable with a suitably chosen cavity and resonant frequency.

  17. Model Evidence of a Superconducting State with a Full Energy Gap in Small Cuprate Islands

    NASA Astrophysics Data System (ADS)

    Black-Schaffer, Annica M.; Golubev, Dmitri S.; Bauch, Thilo; Lombardi, Floriana; Fogelström, Mikael

    2013-05-01

    We investigate subdominant order parameters stabilizing at low temperatures in nanoscale high-Tc cuprate islands, motivated by the recent observation of a fully gapped state in nanosized YBa2Cu3O7-δ [D. Gustafsson et al., Nature Nanotech. 8, 25 (2013)]. Using complementary quasiclassical and tight-binding Bogoliubov-de Gennes methods, we show on distinctly different properties dependent on the symmetry being dx2-y2+is or dx2-y2+idxy. We find that a surface-induced dx2-y2+is phase creates a global spectroscopic gap which increases with an applied magnetic field, consistent with experimental observation.

  18. Short range smectic order driving long range nematic order: Example of cuprates

    DOE PAGESBeta

    Markiewicz, R. S.; Lorenzana, J.; Seibold, G.; Bansil, A.

    2016-01-27

    We present a model for describing the combined presence of nematic and ‘smectic’ or stripe-like orders seen in recent scanning tunneling microscopy (STM) experiments on cuprates. The smectic order is treated as an electronic charge density wave with an associated Peierls distortion or a ‘Pomeranchuk wave’. This primary order is restricted to nanoscale domains by disorder effects, while the secondary coupling to strain generates the nematic order with a considerably longer range. Lastly, a variety of experimental results are shown to be consistent with our theoretical predictions.

  19. Towards material-specific simulations of high-temperature superconducting cuprates

    NASA Astrophysics Data System (ADS)

    Schulthess, Thomas

    2006-03-01

    Simulations of high-temperature superconducting (HTSC) cuprates have typically fallen into two categories: (1) studies of generic models such as the two-dimensional (2D) Hubbard model, that are believed to capture the essential physics necessary to describe the superconducting state, and, (2) first principles electronic structure calculations that are based on the local density approximation (LDA) to density functional theory (DFT) and lead to materials specific models. With advent of massibely parallel vector supercomputers, such as the Cray X1E at ORNL, and cluster algorithms such as the Dynamical Cluster Approximation (DCA), it is now possible to systematically solve the 2D Hubbard model with Quantum Monte Carol (QMC) simulations and to establish that the model indeed describes d-wave superconductivity [1]. Furthermore, studies of a multi-band model with input parameters generated from LDA calculations demonstrate that the existence of a superconducting transition is very sensitive to the underlying band structure [2]. Application of the LDA to transition metal oxides is, however, hampered by spurious self-interactions that particularly affects localized orbitals. Here we apply the self-interaction corrected local spin-density method (SIC-LSD) to describe the electronic structure of the cuprates. It was recently applied with success to generate input parameters for simple models of Mn doped III-V semiconductors [3] and is known to properly describe the antiferromagnetic insulating ground state of the parent compounds of the HTSC cuprates. We will discus the models for HTSC cuprates derived from the SIC-LSD study and how the differences to the well-known LDA results impact the QMC-DCA simulations of the magnetic and superconducting properties. [1] T. A. Maier, M. Jarrell, T. C. Schulthess, P. R. C. Kent, and J. B. White, Phys. Rev. Lett. 95, 237001 (2005). [2] P. Kent, A. Macridin, M. Jarrell, T. Schulthess, O. Andersen, T. Dasgupta, and O. Jepsen, Bulletin of

  20. The Doping Dependence of the Ground State in the Electron-doped Cuprates

    NASA Astrophysics Data System (ADS)

    Greene, Richard L.

    2004-03-01

    The mechanism behind high-temperature superconductivity in the cuprates is not yet determined. Understanding the nature of the normal ground state at various dopings is important for the ultimate determination of the mechanism. Some theories suggest that excitations associated with a doping-dependent quantum phase transition (QPT) are an essential ingredient. So far the evidence for a QPT in the cuprates has been indirect and inconclusive. The electron-doped cuprates offer a distinct advantage over their hole-doped counterparts because the maximum critical magnetic field (H_c2) necessary to access the T=0 normal state is less than 10T. Here, I will present comprehensive measurements of the low-temperature (0.35K to 20K) ab-plane resistivity and Hall effect in the normal state (H>H_c2) of the electron-doped cuprate Pr_2-xCe_xCuO4 (PCCO) as a function of Ce doping. These measurements [1] strongly suggest a quantum critical point at x_c=0.165±0.005 with an associated quantum fluctuation regime at higher temperatures and at nearby dopings. I will also present tunneling results which show that a normal state pseudogap, of unknown origin, disappears near the same doping [2]. The nature of the QPT cannot be determined from our measurements but other results [3] on PCCO suggest an antiferromagnetic-metal to paramagnetic- metal phase transition. I will also report low-temperature specific heat and Raman scattering data in the superconducting state, which show that the superconducting gap anisotropy changes near the critical doping x_c. [1] Y. Dagan et al., cond-mat/0310475. [2] A. Biswas et al., Phys. Rev. B64, 104519 (2001); L. Alff et al., Nature 422, 698 (2003. [3] J. Sonier et al., Phys. Rev. Lett. 91, 147002 (2003); M. Fujita et al., cond-mat/0311269. In collaboration with Y. Dagan, H. Balci, G. Blumberg, C. Kendziora, and M.M.Qazilbash. Support from the NSF under DMR-0102350.

  1. Theory of high-T{sub c} cuprates based on experimental evidence.

    SciTech Connect

    Abrikosov, A. A.

    1999-08-17

    A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of T{sub c}, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc.

  2. Short range smectic order driving long range nematic order: example of cuprates

    PubMed Central

    Markiewicz, R. S.; Lorenzana, J.; Seibold, G.; Bansil, A.

    2016-01-01

    We present a model for describing the combined presence of nematic and ‘smectic’ or stripe-like orders seen in recent scanning tunneling microscopy (STM) experiments on cuprates. The smectic order is treated as an electronic charge density wave with an associated Peierls distortion or a ‘Pomeranchuk wave’. This primary order is restricted to nanoscale domains by disorder effects, while the secondary coupling to strain generates the nematic order with a considerably longer range. A variety of experimental results are shown to be consistent with our theoretical predictions. PMID:26813579

  3. Theory of High-T{sub c} Superconducting Cuprates Based on Experimental Evidence

    DOE R&D Accomplishments Database

    Abrikosov, A. A.

    1999-12-10

    A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of T{sub c}, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc.

  4. Earth Wisdom.

    ERIC Educational Resources Information Center

    Van Matre, Steve

    1985-01-01

    In our human-centered ignorance and arrogance we are rapidly destroying the earth. We must start helping people understand the big picture of ecological concepts. What these concepts mean for our own lives and how we must begin to change our lifestyles in order to live more harmoniously with the earth. (JHZ)

  5. Earth tides

    SciTech Connect

    Harrison, J.C.

    1984-01-01

    Nineteen papers on gravity, tilt, and strain tides are compiled into this volume. Detailed chapters cover the calculation of the tidal forces and of the Earth's response to them, as well as actual observations of earth tides. Partial Contents: On Earth tides. The tidal forces: Tidal Forces. New Computations of the Tide-Generating Potential. Corrected Tables of Tidal Harmonics. The Theory of Tidal Deformations. Body Tides on an Elliptical, Rotating, Elastic and Oceanless Earth, Deformation of the Earth by Surface Loads. Gravimetric Tidal Loading Computed from Integrated Green's Functions. Tidal Friction in the Solid Earth. Loading Tides Versus Body Tides. Lunar Tidal Acceleration from Earth Satellite Orbit Analysis. Observations: gravity. Tidal Gravity in Britain: Tidal Loading and the Spatial Distribution of the Marine Tide. Tidal Loading along a Profile Europe-East Africa-South Asia-Australia and the Pacific Ocean. Detailed Gravity-Tide Spectrum between One and Four Cycles per Day. Observations: tilt and strain. Cavity and Topographic Effects in Tilt and Strain Measurement. Observations of Local Elastic Effects on Earth Tide Tilts and Strains.

  6. Rainbow Earth.

    ERIC Educational Resources Information Center

    Arizona State Dept. of Library and Archives, Phoenix.

    The environment is a great concern in the 1990s, and everyone needs to work at maintaining our planet. The 1992 Arizona State Library Reading Program, "Rainbow Earth," provides children with many techniques they can use to help the Earth. This reading program guide provides information on the following: goals, objectives, and evaluation; getting…

  7. Quasi-particles ultrafastly releasing kink bosons to form Fermi arcs in a cuprate superconductor.

    PubMed

    Ishida, Y; Saitoh, T; Mochiku, T; Nakane, T; Hirata, K; Shin, S

    2016-01-01

    In a conventional framework, superconductivity is lost at a critical temperature (Tc) because, at higher temperatures, gluing bosons can no longer bind two electrons into a Cooper pair. In high-Tc cuprates, it is still unknown how superconductivity vanishes at Tc. We provide evidence that the so-called ≲ 70-meV kink bosons that dress the quasi-particle excitations are playing a key role in the loss of superconductivity in a cuprate. We irradiated a 170-fs laser pulse on Bi2Sr2CaCu2O(8+δ) and monitored the responses of the superconducting gap and dressed quasi-particles by time- and angle-resolved photoemission spectroscopy. We observe an ultrafast loss of superconducting gap near the d-wave node, or light-induced Fermi arcs, which is accompanied by spectral broadenings and weight redistributions occurring within the kink binding energy. We discuss that the underlying mechanism of the spectral broadening that induce the Fermi arc is the undressing of quasi-particles from the kink bosons. The loss mechanism is beyond the conventional framework, and can accept the unconventional phenomena such as the signatures of Cooper pairs remaining at temperatures above Tc. PMID:26728626

  8. Random field disorder and charge order driven quantum oscillations in cuprates

    NASA Astrophysics Data System (ADS)

    Russo, Antonio; Chakravarty, Sudip

    2016-03-01

    In the pseudogap regime of the cuprates, a period-2 charge order breaks a Z2 symmetry, reflecting a broken translational symmetry. Therefore, the interaction of charge order and quenched disorder due to potential scattering, can, in principle, be treated as a random field Ising model. A numerical analysis of the ground state of such a random field Ising model reveals local, glassy dynamics in both two and three dimensions. The dynamics are treated in the glassy limit as a heat bath which couples to the itinerant electrons, leading to an unusual electronic non-Fermi-liquid. If the dynamics are strong enough, the electron spectral function has no quasiparticle peak and the effective mass diverges at the Fermi surface, precluding quantum oscillations. In contrast to charge density, d -density wave order (reflecting staggered circulating currents) does not directly couple to potential disorder, allowing it to support quantum oscillations. At fourth order in Landau theory, there is a term consisting of the square of the d -density wave order parameter, and the square of the charge order. This coupling could induce parasitic charge order, which may be weak enough for the Fermi liquid behavior to remain uncorrupted. Here, we argue that this distinction must be made clear, as one interprets quantum oscillations in cuprates.

  9. Change of carrier density at the pseudogap critical point of a cuprate superconductor.

    PubMed

    Badoux, S; Tabis, W; Laliberté, F; Grissonnanche, G; Vignolle, B; Vignolles, D; Béard, J; Bonn, D A; Hardy, W N; Liang, R; Doiron-Leyraud, N; Taillefer, Louis; Proust, Cyril

    2016-03-10

    The pseudogap is a partial gap in the electronic density of states that opens in the normal (non-superconducting) state of cuprate superconductors and whose origin is a long-standing puzzle. Its connection to the Mott insulator phase at low doping (hole concentration, p) remains ambiguous and its relation to the charge order that reconstructs the Fermi surface at intermediate doping is still unclear. Here we use measurements of the Hall coefficient in magnetic fields up to 88 tesla to show that Fermi-surface reconstruction by charge order in the cuprate YBa2Cu3Oy ends sharply at a critical doping p = 0.16 that is distinctly lower than the pseudogap critical point p* = 0.19 (ref. 11). This shows that the pseudogap and charge order are separate phenomena. We find that the change in carrier density n from n = 1 + p in the conventional metal at high doping (ref. 12) to n = p at low doping (ref. 13) starts at the pseudogap critical point. This shows that the pseudogap and the antiferromagnetic Mott insulator are linked. PMID:26901870

  10. Emergence of Complex States in CMR Manganites and High-Tc Cuprates

    NASA Astrophysics Data System (ADS)

    Dagotto, Elbio

    2005-03-01

    Recent developments in the context of theory and experiments for manganites and cuprates will be discussed. It will be argued that the presence of nanoscale phase separation is at the heart of the colossal magnetoresistance phenomenon [1]. Simulation results support this view, as well as experimental data. These effects are not limited to manganites, but they may appear in other compounds as well, such as the high-Tc cuprates. New results will be presented in this area, on the phenomenological competition between antiferromagnetism and d-wave superconductivity, suggesting the possibility of ``colossal'' effects in this context [2]. This is compatible with the recent discovery of ``giant proximity effects'' in Cu-oxides [3]. All this suggests that clustered or mixed-phase states could form a new paradigm for the understanding of compounds in condensed matter physics. Work in collaboration with G. Alvarez, M. Mayr, A. Moreo, C. Sen, and I. Sergienko, supported by NSF DMR. [1] A. Moreo et al., Science 283, 2034 (1999); E.D., T. Hotta and A. Moreo, Physics Reports 344,1 (2001); E.D., ``Nanoscale Phase Separation and Colossal Magnetoresistance'', Springer-Verlag, 2002. [2] G. Alvarez et al., cond-mat/0401474, PRB to appear. [3] I. Bozovic et al., Phys. Rev. Lett. 93, 157002 (2004)

  11. The Meissner effect in a strongly underdoped cuprate above its critical temperature.

    PubMed

    Morenzoni, Elvezio; Wojek, Bastian M; Suter, Andreas; Prokscha, Thomas; Logvenov, Gennady; Božović, Ivan

    2011-01-01

    The Meissner effect and associated perfect 'bulk' diamagnetism together with zero resistance and gap opening are characteristic features of the superconducting state. In the pseudogap state of cuprates, unusual diamagnetic signals and anomalous proximity effects have been detected, but a Meissner effect has never been observed. Here we probe the local diamagnetic response in the normal state of an underdoped La(1.94)Sr(0.06)CuO(4) layer (T(c)'≤5 K), which is brought into close contact with two nearly optimally doped La(1.84)Sr(0.16)CuO(4) layers (T(c)≈32 K). We show that the entire 'barrier' layer of thickness, much larger than the typical c axis coherence lengths of cuprates, exhibits a Meissner effect at temperatures above T(c)' but below T(c). The temperature dependence of the effective penetration depth and superfluid density in different layers indicates that superfluidity with long-range phase coherence is induced in the underdoped layer by the proximity to optimally doped layers, but this induced order is sensitive to thermal excitation. PMID:21505428

  12. The Meissner effect in a strongly underdoped cuprate above its critical temperature

    PubMed Central

    Morenzoni, Elvezio; Wojek, Bastian M.; Suter, Andreas; Prokscha, Thomas; Logvenov, Gennady; Božović, Ivan

    2011-01-01

    The Meissner effect and associated perfect 'bulk' diamagnetism together with zero resistance and gap opening are characteristic features of the superconducting state. In the pseudogap state of cuprates, unusual diamagnetic signals and anomalous proximity effects have been detected, but a Meissner effect has never been observed. Here we probe the local diamagnetic response in the normal state of an underdoped La1.94Sr0.06CuO4 layer (Tc′≤5 K), which is brought into close contact with two nearly optimally doped La1.84Sr0.16CuO4 layers (Tc≈32 K). We show that the entire 'barrier' layer of thickness, much larger than the typical c axis coherence lengths of cuprates, exhibits a Meissner effect at temperatures above Tc′ but below Tc. The temperature dependence of the effective penetration depth and superfluid density in different layers indicates that superfluidity with long-range phase coherence is induced in the underdoped layer by the proximity to optimally doped layers, but this induced order is sensitive to thermal excitation. PMID:21505428

  13. Single reconstructed Fermi surface pocket in an underdoped single-layer cuprate superconductor

    NASA Astrophysics Data System (ADS)

    Chan, M. K.; Harrison, N.; McDonald, R. D.; Ramshaw, B. J.; Modic, K. A.; Barišić, N.; Greven, M.

    2016-07-01

    The observation of a reconstructed Fermi surface via quantum oscillations in hole-doped cuprates opened a path towards identifying broken symmetry states in the pseudogap regime. However, such an identification has remained inconclusive due to the multi-frequency quantum oscillation spectra and complications accounting for bilayer effects in most studies. We overcome these impediments with high-resolution measurements on the structurally simpler cuprate HgBa2CuO4+δ (Hg1201), which features one CuO2 plane per primitive unit cell. We find only a single oscillatory component with no signatures of magnetic breakdown tunnelling to additional orbits. Therefore, the Fermi surface comprises a single quasi-two-dimensional pocket. Quantitative modelling of these results indicates that a biaxial charge density wave within each CuO2 plane is responsible for the reconstruction and rules out criss-crossed charge stripes between layers as a viable alternative in Hg1201. Lastly, we determine that the characteristic gap between reconstructed pockets is a significant fraction of the pseudogap energy.

  14. The Meissner effect in a Strongly Underdoped Cuprate Above its Critical Temperature

    SciTech Connect

    Morenzoni, E.; Bozovic, I.; Wojek, B.M.; Suter, A.; Prokscha, T.; Logvenov, G.

    2011-04-01

    The Meissner effect and associated perfect 'bulk' diamagnetism together with zero resistance and gap opening are characteristic features of the superconducting state. In the pseudogap state of cuprates, unusual diamagnetic signals and anomalous proximity effects have been detected, but a Meissner effect has never been observed. Here we probe the local diamagnetic response in the normal state of an underdoped La{sub 1.94}Sr{sub 0.06}CuO{sub 4} layer (T'{sub c} {le} 5 K), which is brought into close contact with two nearly optimally doped La{sub 1.84}Sr{sub 0.16}CuO{sub 4} layers (T{sub c} {approx} 32 K). We show that the entire 'barrier' layer of thickness, much larger than the typical c axis coherence lengths of cuprates, exhibits a Meissner effect at temperatures above T{sub c}' but below T{sub c}. The temperature dependence of the effective penetration depth and superfluid density in different layers indicates that superfluidity with long-range phase coherence is induced in the underdoped layer by the proximity to optimally doped layers, but this induced order is sensitive to thermal excitation.

  15. Possible enhancements of AFM spin-fluctuations in high-TC cuprates

    NASA Astrophysics Data System (ADS)

    Jarlborg, Thomas

    2009-03-01

    Ab-initio band calculations for high-TC cuprates, together with modelling based of a free electron like band, show a strong interaction between anti-ferromagnetic (AFM) spin waves and periodic lattice distortions as for phonons, even though this type of spin-phonon coupling (SPC) is underestimated in calculations using the local density approximation. The SPC has a direct influence on the properties of the HTC cuprates and it can explain many observations. The strongest effects are seen for modulated waves in the CuO bond direction, and a band gap is formed near the X,Y points, but unusal band dispersion (like ``waterfalls'') might also be induced below the Fermi energy (EF) in the diagonal direction. The band results are used to propose different ways of increasing AFM spin-fluctuations locally, and to have a higher density-of-states (DOS) at EF. Static potential modulations, via periodic distribution of dopants or lattice distortions, can be tuned to increase the DOS. This opens for possibilities to enhance coupling for spin fluctuations (λsf) and superconductivity. The exchange enhancement is in general increased near a surface, which suggests a tendency towards static spin configurations. The sensivity of the band results to corrections of the local density potential are discussed.

  16. Nodal bilayer-splitting controlled by spin-orbit interactions in underdoped high-Tc cuprates

    DOE PAGESBeta

    Harrison, N.; Ramshaw, B. J.; Shekhter, A.

    2015-06-03

    The highest superconducting transition temperatures in the cuprates are achieved in bilayer and trilayer systems, highlighting the importance of interlayer interactions for high Tc. It has been argued that interlayer hybridization vanishes along the nodal directions by way of a specific pattern of orbital overlap. Recent quantum oscillation measurements in bilayer cuprates have provided evidence for a residual bilayer-splitting at the nodes that is sufficiently small to enable magnetic breakdown tunneling at the nodes. Here we show that several key features of the experimental data can be understood in terms of weak spin-orbit interactions naturally present in bilayer systems, whosemore » primary effect is to cause the magnetic breakdown to be accompanied by a spin flip. These features can now be understood to include the equidistant set of three quantum oscillation frequencies, the asymmetry of the quantum oscillation amplitudes in c-axis transport compared to ab-plane transport, and the anomalous magnetic field angle dependence of the amplitude of the side frequencies suggestive of small effective g-factors. We suggest that spin-orbit interactions in bilayer systems can further affect the structure of the nodal quasiparticle spectrum in the superconducting phase. PACS numbers: 71.45.Lr, 71.20.Ps, 71.18.+y« less

  17. Origins of large critical temperature variations in single-layer cuprates

    SciTech Connect

    Palczewski, A.D.; Kondo, T.; Khasanov, R.; Kolesikov, N.N.; Timonina; Rotenberg, E.; Ohta, T.; Bendounan, A.; Sassa, Y.; Fedorov, A.; Paihes, S.; Santander-Syro, A.F.; Chang, J.; Shi, M.; Mesot, J.; Fretwell, H.M.; Kaminski, A.

    2008-08-26

    We study the electronic structures of two single-layer superconducting cuprates, Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} (Tl2201) and (Bi{sub 1.35}Pb{sub 0.85}) (Sr{sub 1.47}La{sub 0.38}) CuO{sub 6+{delta}} (Bi2201) which have very different maximum critical temperatures (90 K and 35 K, respectively) using angular-resolved photoemission spectroscopy (ARPES). We are able to identify two main differences in their electronic properties. First, the shadow band that is present in double-layer and low T{sub c,max} single-layer cuprates is absent in Tl2201. Recent studies have linked the shadow band to structural distortions in the lattice and the absence of these in Tl2201 may be a contributing factor in its T{sub c,max}. Second, Tl2201's Fermi surface (FS) contains long straight parallel regions near the antinode, while in Bi2201 the antinodal region is much more rounded. Since the size of the superconducting gap is largest in the antinodal region, differences in the band dispersion at the antinode may play a significant role in the pairing and therefore affect the maximum transition temperature.

  18. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    NASA Astrophysics Data System (ADS)

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; He, Y.; Shen, Z. X.; Yoshida, Y.; Eisaki, H.; Mou, C. Y.; Chen, C. T.; Huang, D. J.

    2016-01-01

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.

  19. Substantial T-dependences of the Cu-NMR relaxation rates in the underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Goto, Atsushi; Shimizu, Tadashi

    2001-03-01

    We discuss two distinct effects observed in the spin-spin relaxation process in the planar Cu sites of the underdoped high-Tc cuprates. One originates from the interlayer spin correlations in bi- and tri-layered CuO2 planes [1,2], which introduce relaxation in addition to that of a single CuO2 plane. These processes become more significant at low T, i.e., in the pseudogap T region [2]. The other is from T1 fluctuations of the nuclear spins in the vicinity of the nucleus of interest [3], which change the characteristic of the relaxation process from a static to a dynamical one. We demonstrate the principal roles of these effects in the underdoped cuprate (HgRe)Ba_2Ca_2Cu_3O8 and show that, although the total 1/T_2G increases with decreasing T, its intraplane contribution decreases as T is reduced in the pseudogap region, as does 1/T_1T [4]. [1] J. Kishine, Thesis, Univ. of Tokyo, 1996. [2] A. Goto and T. Shimizu, Phys. Rev. B 57 (1998) 7977. [3] R. E. Walstedt and S-W. Cheong, Phys. Rev. B 51 (1995) 3163. [4] A. Goto et al., Phys. Rev. B 59 (1999) R14169.

  20. Self-optimized superconductivity attainable by interlayer phase separation at cuprate interfaces.

    PubMed

    Misawa, Takahiro; Nomura, Yusuke; Biermann, Silke; Imada, Masatoshi

    2016-07-01

    Stabilizing superconductivity at high temperatures and elucidating its mechanism have long been major challenges of materials research in condensed matter physics. Meanwhile, recent progress in nanostructuring offers unprecedented possibilities for designing novel functionalities. Above all, thin films of cuprate and iron-based high-temperature superconductors exhibit remarkably better superconducting characteristics (for example, higher critical temperatures) than in the bulk, but the underlying mechanism is still not understood. Solving microscopic models suitable for cuprates, we demonstrate that, at an interface between a Mott insulator and an overdoped nonsuperconducting metal, the superconducting amplitude is always pinned at the optimum achieved in the bulk, independently of the carrier concentration in the metal. This is in contrast to the dome-like dependence in bulk superconductors but consistent with the astonishing independence of the critical temperature from the carrier density x observed at the interfaces of La2CuO4 and La2-x Sr x CuO4. Furthermore, we identify a self-organization mechanism as responsible for the pinning at the optimum amplitude: An emergent electronic structure induced by interlayer phase separation eludes bulk phase separation and inhomogeneities that would kill superconductivity in the bulk. Thus, interfaces provide an ideal tool to enhance and stabilize superconductivity. This interfacial example opens up further ways of shaping superconductivity by suppressing competing instabilities, with direct perspectives for designing devices. PMID:27482542

  1. Single reconstructed Fermi surface pocket in an underdoped single-layer cuprate superconductor

    PubMed Central

    Chan, M. K.; Harrison, N.; McDonald, R. D.; Ramshaw, B. J.; Modic, K. A.; Barišić, N.; Greven, M.

    2016-01-01

    The observation of a reconstructed Fermi surface via quantum oscillations in hole-doped cuprates opened a path towards identifying broken symmetry states in the pseudogap regime. However, such an identification has remained inconclusive due to the multi-frequency quantum oscillation spectra and complications accounting for bilayer effects in most studies. We overcome these impediments with high-resolution measurements on the structurally simpler cuprate HgBa2CuO4+δ (Hg1201), which features one CuO2 plane per primitive unit cell. We find only a single oscillatory component with no signatures of magnetic breakdown tunnelling to additional orbits. Therefore, the Fermi surface comprises a single quasi-two-dimensional pocket. Quantitative modelling of these results indicates that a biaxial charge density wave within each CuO2 plane is responsible for the reconstruction and rules out criss-crossed charge stripes between layers as a viable alternative in Hg1201. Lastly, we determine that the characteristic gap between reconstructed pockets is a significant fraction of the pseudogap energy. PMID:27448102

  2. Self-optimized superconductivity attainable by interlayer phase separation at cuprate interfaces

    PubMed Central

    Misawa, Takahiro; Nomura, Yusuke; Biermann, Silke; Imada, Masatoshi

    2016-01-01

    Stabilizing superconductivity at high temperatures and elucidating its mechanism have long been major challenges of materials research in condensed matter physics. Meanwhile, recent progress in nanostructuring offers unprecedented possibilities for designing novel functionalities. Above all, thin films of cuprate and iron-based high-temperature superconductors exhibit remarkably better superconducting characteristics (for example, higher critical temperatures) than in the bulk, but the underlying mechanism is still not understood. Solving microscopic models suitable for cuprates, we demonstrate that, at an interface between a Mott insulator and an overdoped nonsuperconducting metal, the superconducting amplitude is always pinned at the optimum achieved in the bulk, independently of the carrier concentration in the metal. This is in contrast to the dome-like dependence in bulk superconductors but consistent with the astonishing independence of the critical temperature from the carrier density x observed at the interfaces of La2CuO4 and La2−xSrxCuO4. Furthermore, we identify a self-organization mechanism as responsible for the pinning at the optimum amplitude: An emergent electronic structure induced by interlayer phase separation eludes bulk phase separation and inhomogeneities that would kill superconductivity in the bulk. Thus, interfaces provide an ideal tool to enhance and stabilize superconductivity. This interfacial example opens up further ways of shaping superconductivity by suppressing competing instabilities, with direct perspectives for designing devices. PMID:27482542

  3. Single reconstructed Fermi surface pocket in an underdoped single-layer cuprate superconductor.

    PubMed

    Chan, M K; Harrison, N; McDonald, R D; Ramshaw, B J; Modic, K A; Barišić, N; Greven, M

    2016-01-01

    The observation of a reconstructed Fermi surface via quantum oscillations in hole-doped cuprates opened a path towards identifying broken symmetry states in the pseudogap regime. However, such an identification has remained inconclusive due to the multi-frequency quantum oscillation spectra and complications accounting for bilayer effects in most studies. We overcome these impediments with high-resolution measurements on the structurally simpler cuprate HgBa2CuO4+δ (Hg1201), which features one CuO2 plane per primitive unit cell. We find only a single oscillatory component with no signatures of magnetic breakdown tunnelling to additional orbits. Therefore, the Fermi surface comprises a single quasi-two-dimensional pocket. Quantitative modelling of these results indicates that a biaxial charge density wave within each CuO2 plane is responsible for the reconstruction and rules out criss-crossed charge stripes between layers as a viable alternative in Hg1201. Lastly, we determine that the characteristic gap between reconstructed pockets is a significant fraction of the pseudogap energy. PMID:27448102

  4. p-Orbital Density Wave with d Symmetry in High-Tc Cuprate Superconductors

    NASA Astrophysics Data System (ADS)

    Tsuchiizu, Masahisa; Yamakawa, Youichi; Kontani, Hiroshi

    Emergence of the nematic density wave is a fundamental unsolved problem in cuprate superconductors. To understand the origin of the nematicity, we employ the recently-developed functional renormalization-group method with high numerical accuracy, and discover the critical development of the p-orbital-density-wave (p-ODW) instability in the strong-spin-fluctuation region. The obtained p-ODW state possesses the key characteristics of the charge ordering pattern in Bi- and Y-based superconductors, such as the wavevector parallel to the nearest Cu-Cu direction, and the d-symmetry form factor with the antiphase correlation between px and py orbitals in the same unit cell. From the beautiful scaling relation between the spin susceptibility and the p-ODW susceptibility, we conclude that the p-ODW is driven by the strong interference between spin and charge fluctuations. It is clarified that the strong charge-spin interference, which is the origin of the nematicity, is the hidden but significant characteristics of the electronic states in cuprate superconductors.

  5. Quasi-particles ultrafastly releasing kink bosons to form Fermi arcs in a cuprate superconductor

    PubMed Central

    Ishida, Y.; Saitoh, T.; Mochiku, T.; Nakane, T.; Hirata, K.; Shin, S.

    2016-01-01

    In a conventional framework, superconductivity is lost at a critical temperature (Tc) because, at higher temperatures, gluing bosons can no longer bind two electrons into a Cooper pair. In high-Tc cuprates, it is still unknown how superconductivity vanishes at Tc. We provide evidence that the so-called ≲70-meV kink bosons that dress the quasi-particle excitations are playing a key role in the loss of superconductivity in a cuprate. We irradiated a 170-fs laser pulse on Bi2Sr2CaCu2O8+δ and monitored the responses of the superconducting gap and dressed quasi-particles by time- and angle-resolved photoemission spectroscopy. We observe an ultrafast loss of superconducting gap near the d-wave node, or light-induced Fermi arcs, which is accompanied by spectral broadenings and weight redistributions occurring within the kink binding energy. We discuss that the underlying mechanism of the spectral broadening that induce the Fermi arc is the undressing of quasi-particles from the kink bosons. The loss mechanism is beyond the conventional framework, and can accept the unconventional phenomena such as the signatures of Cooper pairs remaining at temperatures above Tc. PMID:26728626

  6. Power-law Optical Conductivity from Unparticles: Application to the Cuprates

    NASA Astrophysics Data System (ADS)

    Limtragool, Kridsanaphong; Phillips, Philip

    We calculate the optical conductivity using several models for unparticle or scale-invariant matter. Within a Gaussian action for unparticles that is gauged with Wilson lines, we find that the conductivity computed from the Kubo formalism with vertex corrections yields no non-trivial deviation from the free-theory result. This result obtains because at the Gaussian level, unparticles are just a superposition of particle fields and hence any transport property must be consistent with free theory. Beyond the Gaussian approach, we adopt the continuous mass formulation of unparticles and calculate the Drude conductivity directly. We show that unparticles in this context can be tailored to yield an algebraic conductivity that scales as ω - 2 / 3 with the associated phase angle between the imaginary and real parts of arctanσ2/σ1 =60° as is seen in the cuprates. Our results indicate that at each frequency in the scaling regime, excitations on all energy scales contribute. Hence, incoherence is at the heart of the power-law in the optical conductivity in strongly correlated systems such as the cuprates. We thank NSF DMR-1461952 for partial funding of this project. KL is supported by a scholarship from the Ministry of Science and Technology, Royal Thai Government. PP thanks the Guggenheim Foundation for a 2015-2016 Fellowship.

  7. Spin-fermion model with overlapping hot spots and charge modulation in cuprates

    NASA Astrophysics Data System (ADS)

    Volkov, Pavel A.; Efetov, Konstantin B.

    We study particle-hole instabilities in the framework of the spin-fermion model. In contrast to previous studies, we assume that adjacent hot spots can overlap due to a shallow dispersion of the electron spectrum in the antinodal region and take the effects of a remnant Coulomb interaction into account. We demonstrate that at sufficiently small values | ɛ (π , 0) - EF | < Γ , where Γ is a characteristic energy of the fermion-fermion interaction due to the paramagnons, the leading particle-hole instability is a d-form factor Fermi surface deformation rather than the charge modulation along the Brillouin zone diagonals. At lower temperatures, we find that the deformed Fermi surface is further unstable to formation of a d-form factor charge density wave (CDW) with a wave vector along one of the Brillouin zone axes. These findings can explain the robustness of this order in hole-doped cuprates. The approximations made are justified by a small parameter that allows one an Eliashberg-like treatment. Comparison with experiments suggests that in many cuprate compounds the prerequisites for the proposed scenario are indeed fulfilled and the results obtained may explain important features of the charge modulations observed recently.

  8. Random field disorder and charge order driven quantum oscillations in cuprates

    NASA Astrophysics Data System (ADS)

    Russo, Antonio; Chakravarty, Sudip

    In the pseudogap regime of the cuprates, charge order breaks a ℤ2 symmetry. Therefore, the interaction of charge order and quenched disorder due to potential scattering, can, in principle, be treated as a random field Ising model. A numerical analysis of the ground state of such a random field Ising model reveals local, glassy dynamics in both 2 D and 3 D . The glassy dynamics are treated as a heat bath which couple to the itinerant electrons, leading to an unusual electronic non-Fermi liquid. If the dynamics are strong enough, the electron spectral function has no quasiparticle peak and the effective mass diverges at the Fermi surface, precluding quantum oscillations. In contrast to charge density, d-density wave order (reflecting staggered circulating currents) does not directly couple to potential disorder, allowing it to support quantum oscillations. At fourth order in Landau theory, there is a term consisting of the square of the d-density wave order parameter, and the square of the charge order. This coupling could induce parasitic charge order, which may be weak enough for the Fermi liquid behavior to remain uncorrupted. Here, we argue that this distinction must be made clear, as one interprets quantum oscillations in cuprates.

  9. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    DOE PAGESBeta

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; et al

    2016-01-22

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast,more » the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.« less

  10. Disentangling Cooper-pair formation above the transition temperature from the pseudogap state in the cuprates

    SciTech Connect

    Kondo, Takeshi; Hamaya, Yoichiro; Palczewski, Ari D.; Takeuchi, Tsunehiro; Wen, J. S.; Xu, Z. J.; Gu, Genda; Schmalian, Joerg; Kaminski, Adam

    2010-12-05

    The discovery of the pseudogap in the cuprates created significant excitement as it was believed to be a signature of pairing, in some cases above room temperature. Indeed, a number of experiments detected phase-fluctuating superconductivity above the transition temperature T{sub c}. However, several recent experiments reported that the pseudogap and superconducting state are characterized by different energy scales and probably compete with each other, leaving open the question of whether the pseudogap is caused by pair formation. Here we report the discovery of a spectroscopic signature of pair formation and demonstrate that in a region commonly referred to as the pseudogap, two distinct states coexist: one that is due to pair formation and persists to an intermediate temperature T{sub pair} < T* and a second - the 'proper' pseudogap - characterized by the loss of spectral weight and anomalies in transport properties that extends up to T*. T{sub pair} has a value around 120-150 K even for materials with very different T{sub c} values and it probably sets a limit on the highest attainable T{sub c} in the cuprates

  11. Disentangling Cooper-pair formation above the transition temperature from the pseudogap state in the cuprates

    SciTech Connect

    Kondo, Takeshi; Hamaya, Yoichiro; Palczewski, Ari D.; Takeuchi, Tsunehiro; Wen, J. S.; Xu, Z. J.; Gu, Genda; Schmalian, Jorg; Kaminski, Adam

    2010-12-05

    The discovery of the pseudogap in the cuprates created significant excitement as it was believed to be a signature of pairing, in some cases above room temperature. Indeed, a number of experiments detected phase-fluctuating superconductivity above the transition temperature T{sub c}. However, several recent experiments reported that the pseudogap and superconducting state are characterized by different energy scales, and probably compete with each other, leaving open the question of whether the pseudogap is caused by pair formation. Here we report the discovery of a spectroscopic signature of pair formation and demonstrate that in a region commonly referred to as the pseudogap, two distinct states coexist: one that is due to pair formation and persists to an intermediate temperature T{sub pair}cuprates.

  12. Magnetic proximity effect at the interface between a cuprate superconductor and an oxide spin valve

    NASA Astrophysics Data System (ADS)

    Ovsyannikov, G. A.; Demidov, V. V.; Khaydukov, Yu. N.; Mustafa, L.; Constantinian, K. Y.; Kalabukhov, A. V.; Winkler, D.

    2016-04-01

    A heterostructure that consists of the YBa2Cu3O7-δ cuprate superconductor and the SrRuO3/La0.7Sr0.3MnO3 ruthenate/manganite spin valve is investigated using SQUID magnetometry, ferromagnetic resonance, and neutron reflectometry. It is shown that a magnetic moment is induced due to the magnetic proximity effect in the superconducting part of the heterostructure, while the magnetic moment in the composite ferromagnetic interlayer is suppressed. The magnetization emerging in the superconductor coincides in order of magnitude with the results of calculations taking into account the induced magnetic moment of Cu atoms because of orbital reconstruction at the interface between the superconductor and the ferromagnet, as well as with the results of the model taking into account the variations in the density of states at a distance on the order of the coherence length in the superconductor. The experimentally obtained characteristic penetration depth of the magnetic moment in the superconductor considerably exceeds the coherence length of the cuprate superconductor, which indicates the predominance of the mechanism of induced magnetic moment of Cu atoms.

  13. Nodal bilayer-splitting controlled by spin-orbit interactions in underdoped high-Tc cuprates

    PubMed Central

    Harrison, N.; Ramshaw, B. J.; Shekhter, A.

    2015-01-01

    The highest superconducting transition temperatures in the cuprates are achieved in bilayer and trilayer systems, highlighting the importance of interlayer interactions for high Tc. It has been argued that interlayer hybridization vanishes along the nodal directions by way of a specific pattern of orbital overlap. Recent quantum oscillation measurements in bilayer cuprates have provided evidence for a residual bilayer-splitting at the nodes that is sufficiently small to enable magnetic breakdown tunneling at the nodes. Here we show that several key features of the experimental data can be understood in terms of weak spin-orbit interactions naturally present in bilayer systems, whose primary effect is to cause the magnetic breakdown to be accompanied by a spin flip. These features can now be understood to include the equidistant set of three quantum oscillation frequencies, the asymmetry of the quantum oscillation amplitudes in c-axis transport compared to ab-plane transport, and the anomalous magnetic field angle dependence of the amplitude of the side frequencies suggestive of small effective g-factors. We suggest that spin-orbit interactions in bilayer systems can further affect the structure of the nodal quasiparticle spectrum in the superconducting phase. PACS numbers: 71.45.Lr, 71.20.Ps, 71.18.+y PMID:26039222

  14. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    PubMed Central

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; He, Y.; Shen, Z. X.; Yoshida, Y.; Eisaki, H.; Mou, C. Y.; Chen, C. T.; Huang, D. J.

    2016-01-01

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors. PMID:26794437

  15. Emergent non-Fermi liquid in the pseudogap phase of the underdoped cuprates

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Markiewicz, R. S.; Bansil, A.

    2010-03-01

    As the cuprates approach the Mott insulator limit, they display a remarkable gossamer-like structure: the near-Fermi level dispersion remains nearly unrenormalized while the corresponding spectral weight tends to vanish at half filling[1]. This unusual behavior cannot be understood by conventional Fermi liquid theory where both features are controlled by a single renormalization factor. We find that while the fluctuation spectrum remains nearly isotropic in cuprates, the competing order pseudogap (here modelled as antiferromagnetism) breaks the crystal symmetry and thus promotes a strong momentum dependence in the self-energy term[2]. At half-filling, this yields an essentially unrenormalized quasiparticle dispersion which approaches the uncorrelated limit, while in sharp contrast the quasiparticle spectral weight renormalizes to zero. These opposing tendencies of dispersion and spectral weight renormalization conspire in such a way that the specific heat remains Fermi liquid like in character at all dopings in accord with experiments. Work supported in part by the USDOE. [1] S. Sahrakorpi, et al., Phys. Rev. B 78, 104513 (2008). [2] T. Das, et al., arXiv:0807.4257.

  16. Exact phase diagram of multi-orbital spin-fermion model for hole doped cuprates

    NASA Astrophysics Data System (ADS)

    Meetei, Oinam Nganba; Fischer, Mark; Lawler, Michael; Paramekanti, Arun; Kim, Eun-Ah

    2015-03-01

    Recent experiments revealing the ubiquitous presence of spin and charge ordered states in hole-doped cuprates have placed the study of broken symmetry states at the center of high Tc superconductivity research. Here we aim to understand the phase diagram of broken symmetry states using a simple model that captures the essence of hole doped cuprates. The model consists of itinerant quantum holes on oxygen p-orbitals coupled to classical Cu spins. It is amenable to sign problem free Monte-Carlo simulation allowing us to study finite temperature properties as well as unbiased determination of ground state spin and charge configuration. As a function of system parameters, we obtain a rich phase diagram. Our analysis provides a transparent and unifying picture for various charge and spin ordered states as arising from frustration of antiferromagnetic order due to hole doping, through exact finite temperature phase diagram of the model. Supported by the U.S. Department of Energy Grant DE-SC0010313.

  17. Change of carrier density at the pseudogap critical point of a cuprate superconductor

    NASA Astrophysics Data System (ADS)

    Badoux, S.; Tabis, W.; Laliberté, F.; Grissonnanche, G.; Vignolle, B.; Vignolles, D.; Béard, J.; Bonn, D. A.; Hardy, W. N.; Liang, R.; Doiron-Leyraud, N.; Taillefer, Louis; Proust, Cyril

    2016-03-01

    The pseudogap is a partial gap in the electronic density of states that opens in the normal (non-superconducting) state of cuprate superconductors and whose origin is a long-standing puzzle. Its connection to the Mott insulator phase at low doping (hole concentration, p) remains ambiguous and its relation to the charge order that reconstructs the Fermi surface at intermediate doping is still unclear. Here we use measurements of the Hall coefficient in magnetic fields up to 88 tesla to show that Fermi-surface reconstruction by charge order in the cuprate YBa2Cu3Oy ends sharply at a critical doping p = 0.16 that is distinctly lower than the pseudogap critical point p* = 0.19 (ref. 11). This shows that the pseudogap and charge order are separate phenomena. We find that the change in carrier density n from n = 1 + p in the conventional metal at high doping (ref. 12) to n = p at low doping (ref. 13) starts at the pseudogap critical point. This shows that the pseudogap and the antiferromagnetic Mott insulator are linked.

  18. η collective mode as A1 g Raman resonance in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Montiel, X.; Kloss, T.; Pépin, C.; Benhabib, S.; Gallais, Y.; Sacuto, A.

    2016-01-01

    We discuss the possible existence of a spin singlet excitation with charge ±2 (η mode) originating the A1 g Raman resonance in cuprate superconductors. This η mode relates the d -wave superconducting singlet pairing channel to a d -wave charge channel. We show that the η boson forms a particle-particle bound state below the 2 Δ threshold of the particle-hole continuum where Δ is the maximum d -wave gap. Within a generalized random phase approximation and Bethe-Salpeter approximation study, we find that this mode has energies similar to the resonance observed with inelastic neutron scattering below the superconducting (SC) coherent peak at 2 Δ in various SC cuprate compounds. We show that it is a very good candidate for the resonance observed in Raman scattering below the 2 Δ peak in the A1 g symmetry. Since the η mode sits in the S =0 channel, it may be observable via Raman, x-ray, or electron energy loss spectroscopy probes.

  19. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates.

    PubMed

    Huang, H Y; Jia, C J; Chen, Z Y; Wohlfeld, K; Moritz, B; Devereaux, T P; Wu, W B; Okamoto, J; Lee, W S; Hashimoto, M; He, Y; Shen, Z X; Yoshida, Y; Eisaki, H; Mou, C Y; Chen, C T; Huang, D J

    2016-01-01

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O(8+δ). Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors. PMID:26794437

  20. Ultrasonic signatures at the superconducting and the pseudogap phase boundaries in YBCO cuprates.

    SciTech Connect

    Shehter, Arkady; Migliori, Albert; Betts, Jonathan B.; Balakirev, Fedor F.; McDonald, Ross David; Riggs, Scott C.; Ramshaw, Brad; Liang, Ruixing; Hardy, Walter N.; Bonn, Doug A.

    2012-08-28

    A major issue in the understanding of cuprate superconductors is the nature of the metallic state from which high temperature superconductivity emerges. Central to this issue is the pseudogap region of the doping-temperature phase diagram that extends from room temperature to the superconducting transition. Although polarized neutron scattering studies hint at magnetic order associated with the pseudogap, there is no clear thermodynamic evidence for a phase boundary. Such evidence has a straightforward physical interpretation, however, it is difficult to obtain over a temperature range wide enough to encompass both the pseudogap and superconducting phases. We address this by measuring the elastic response of detwinned single crystals, an underdoped YBCO{sub 6.60} with superconducting transition at T{sub c} = 61.6K and a slightly overdoped YBCO{sub 6.98} with T{sub c} = 88.0K. We observe a discontinuity in the elastic moduli across the superconducting transition. Its magnitude requires that pair formation is coincident with superconducting coherence (the onset of the Meissner effect). For both crystals the elastic response reveals a phase transition at the pseudogap boundary. In slightly overdoped YBCO that transition is 20K below T{sub c}, extending the pseudogap phase boundary inside the superconducting dome. This supports a description of the metallic state in cuprates where a pseudogap phase boundary evolves into a quantum critical point masked by the superconducting dome.

  1. In-plane resistivity anisotropy in underdoped cuprates due to scattering by charge and spin fluctuations

    NASA Astrophysics Data System (ADS)

    Schütt, Michael; Fernandes, Rafael M.

    2015-03-01

    The existence of strong in-plane electronic anisotropies in underdoped cuprates has been reported by a variety of experimental probes, such as transport measurements, scanning tunneling microscopy, and x-ray and neutron scattering. Understanding the origin of these anisotropies and their interplay is fundamental to elucidate the role played by electronic nematicity in the phase diagram of the cuprates. Here we employ a Boltzmann equation approach to investigate the resistivity anisotropy due to scattering by anisotropic spin and charge fluctuations. We show that while spin fluctuations give rise to larger resistivity along the a direction, charge fluctuations promote larger resistivity along the b direction. Because anisotropic charge and spin fluctuations compete, these behaviors give rise to a particular dependence of the resistivity anisotropy with doping, which is consistent with transport experiments performed in YBa2Cu3O7. We discuss the important role played by the CuO chains in YBCO to select the observed type of nematic domains, and propose transport measurements in strained HgBa2CuO4 and Bi2Sr2CaCu2O8 to shed light on the interplay between anisotropic fluctuations and anisotropic resistivity. MS acknowledges the support from the Humboldt Foundation. RMF is supported by the Department of Energy under Award Number DE-SC0012336.

  2. Vestigial nematicity from spin and/or charge order in the cuprates

    NASA Astrophysics Data System (ADS)

    Nie, Laimei; Maharaj, Akash; Fradkin, Eduardo; Kivelson, Steven

    Nematic order (C4 rotation symmetry breaking) has manifested itself in a variety of materials in the cuprates family, yet its origin remains debatable, with possible links to lattice, charge, and spin degrees of freedom across different doping regimes. We propose an effective field theory of a layered system with incommensurate, intertwined spin- and charge-density wave (SDW and CDW) orders, each of which consists of two components related by C4 rotations. Using a variational free energy approach, we study the growth of the associated nematicity from partially melting those density waves by either increasing temperature or adding quenched disorder. Under the assumption that the zero-disorder, zero-interaction SDW transition temperature is higher than CDW at small doping (and vice versa for large doping), we find that for the general case with finite disorder and interactions there is a universal nematic transition across the entire doping range, accompanied by SDW and CDW transitions (or strong fluctuations at large enough disorder) at lower temperatures. We also discuss the issues concerning the difference between La-based materials and the other hole-doped cuprates.

  3. Atomic-scale electronic structure of the cuprate d-symmetry form factor density wave state

    NASA Astrophysics Data System (ADS)

    Hamidian, M. H.; Edkins, S. D.; Kim, Chung Koo; Davis, J. C.; MacKenzie, A. P.; Eisaki, H.; Uchida, S.; Lawler, M. J.; Kim, E.-A.; Sachdev, S.; Fujita, K.

    2016-02-01

    Research on high-temperature superconducting cuprates is at present focused on identifying the relationship between the classic `pseudogap’ phenomenon and the more recently investigated density wave state. This state is generally characterized by a wavevector Q parallel to the planar Cu-O-Cu bonds along with a predominantly d-symmetry form factor (dFF-DW). To identify the microscopic mechanism giving rise to this state, one must identify the momentum-space states contributing to the dFF-DW spectral weight, determine their particle-hole phase relationship about the Fermi energy, establish whether they exhibit a characteristic energy gap, and understand the evolution of all these phenomena throughout the phase diagram. Here we use energy-resolved sublattice visualization of electronic structure and reveal that the characteristic energy of the dFF-DW modulations is actually the `pseudogap’ energy Δ1. Moreover, we demonstrate that the dFF-DW modulations at E = -Δ1 (filled states) occur with relative phase π compared to those at E = Δ1 (empty states). Finally, we show that the conventionally defined dFF-DW Q corresponds to scattering between the `hot frontier’ regions of momentum-space beyond which Bogoliubov quasiparticles cease to exist. These data indicate that the cuprate dFF-DW state involves particle-hole interactions focused at the pseudogap energy scale and between the four pairs of `hot frontier’ regions in momentum space where the pseudogap opens.

  4. Phase separation of electrons strongly coupled with phonons in cuprates and manganites

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sasha

    2009-03-01

    Recent advanced Monte Carlo simulations have not found superconductivity and phase separation in the Hubbard model with on-site repulsive electron-electron correlations. I argue that microscopic phase separations in cuprate superconductors and colossal magnetoresistance (CMR) manganites originate from a strong electron-phonon interaction (EPI) combined with unavoidable disorder. Attractive electron correlations, caused by an almost unretarded EPI, are sufficient to overcome the direct inter-site Coulomb repulsion in these charge-transfer Mott-Hubbard insulators, so that low energy physics is that of small polarons and small bipolarons. They form clusters localized by disorder below the mobility edge, but propagate as the Bloch states above the mobility edge. I identify the Froehlich EPI as the most essential for pairing and phase separation in superconducting layered cuprates. The pairing of oxygen holes into heavy bipolarons in the paramagnetic phase (current-carrier density collapse (CCDC)) explains also CMR and high and low-resistance phase coexistence near the ferromagnetic transition of doped manganites.

  5. Electronic structure of hole centers in CuO2 planes of cuprates

    NASA Astrophysics Data System (ADS)

    Moskvin, A. S.; Panov, Yu. D.

    2011-03-01

    A theoretical analysis and a large amount of experimental data indicate that the structure of the valence hole states in doped cuprates is more complicated than assumed in the simple Zhang-Rice singlet model. In fact, we are dealing with a competition between a hybrid Cu3d -O2pb1g∝dx2-y2-state and purely oxygen nonbonding states with a2g- and eux ,y∝px ,y-symmetries. Thus, as a cluster analog of a Cu3+ ion, the ground state of a non-Zhang-Rice CuO45- hole center of this sort should be described by complicated A1g1-B2g1,3-Eu1,3 multiplet with a set of charge, orbital, and spin order parameters, some of which are well known (e.g., spin moment or "ferromagnetic" Ising orbital momentum localized on oxygen ions) while others are unconventional or hidden (e.g., "antiferromagnetic" ordering of Ising orbital momenta localized on four oxygen atoms or a combined spin-orbital-quadrupole ordering). The non-Zhang-Rice CuO45- centers are actually singlet-triplet pseudo-Jahn-Teller centers with strong vibron coupling to the lattice. The complicated structure of the ground-state multiplet of the hole centers shows up in many of the unusual properties of doped cuprates, in particular, their pseudo-gap phase.

  6. A simple model for normal state in- and out-of-plane resistivities of hole doped cuprates

    NASA Astrophysics Data System (ADS)

    Naqib, S. H.; Azam, M. Afsana; Uddin, M. Borhan; Cole, J. R.

    2016-05-01

    The highly anisotropic and qualitatively different nature of the normal state in- and out-of-plane charge dynamics in high-Tc cuprates cannot be accommodated within the conventional Boltzmann transport theory. The variation of in-plane and out-of-plane resistivities with temperature and hole content are anomalous and cannot be explained by Fermi-liquid theory. In this study, we have proposed a simple phenomenological model for the dc resistivity of cuprates by incorporating two firmly established generic features of all hole doped cuprate superconductors-(i) the pseudogap in the quasiparticle energy spectrum and (ii) the T-linear resistivity at high temperatures. This T-linear behavior over an extended temperature range can be attributed to a quantum criticality, affecting the electronic phase diagram of cuprates. Experimental in-plane and out-of-plane resistivities (ρp(T) and ρc(T), respectively) of double-layer Y(Ca)123 have been analyzed using the proposed model. This phenomenological model describes the temperature and the hole content dependent resistivity over a wide range of temperature and hole content, p. The characteristic PG energy scale, εg(p), extracted from the analysis of the resistivity data, agrees quite well with those found in variety of other experiments. Various other extracted parameters from the analysis of ρp(T) and ρc(T) data showed systematic trends with changing hole concentration. We have discussed important features found from the analysis in detail in this paper.

  7. Discover Earth

    NASA Technical Reports Server (NTRS)

    Steele, Colleen

    1996-01-01

    Discover Earth is a NASA-funded project for teachers of grades 5-12 who want to expand their knowledge of the Earth system, and prepare to become master teachers who promote Earth system science in their own schools, counties, and throughout their state. Participants from the following states are invited to apply: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Washington, DC. Teachers selected for the project participate in a two-week summer workshop conducted at the University of Maryland, College Park; develop classroom-ready materials during the workshop for broad dissemination; conduct a minimum of two peer training activities during the coming school year; and participate in other enrichment/education opportunities as available and desired. Discover Earth is a team effort that utilizes expertise from a range of contributors, and balances science content with hands-on classroom applications.

  8. Discover Earth

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Discover Earth is a NASA-funded project for teachers of grades 5-12 who want to expand their knowledge of the Earth system, and prepare to become master teachers who promote Earth system science in their own schools, counties, and throughout their state. Participants from the following states are invited to apply: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Washington, DC. Teachers selected for the project participate in a two-week summer workshop conducted at the University of Maryland, College Park; develop classroom-ready materials during the workshop for broad dissemination; conduct a minimum of two peer training activities during the coming school year; and participate in other enrichment/education opportunities as available and desired. Discover Earth is a team effort that utilizes expertise from a range of contributors, and balances science content with hands-on classroom applications.

  9. Earth Rotation

    NASA Technical Reports Server (NTRS)

    Dickey, Jean O.

    1995-01-01

    The study of the Earth's rotation in space (encompassing Universal Time (UT1), length of day, polar motion, and the phenomena of precession and nutation) addresses the complex nature of Earth orientation changes, the mechanisms of excitation of these changes and their geophysical implications in a broad variety of areas. In the absence of internal sources of energy or interactions with astronomical objects, the Earth would move as a rigid body with its various parts (the crust, mantle, inner and outer cores, atmosphere and oceans) rotating together at a constant fixed rate. In reality, the world is considerably more complicated, as is schematically illustrated. The rotation rate of the Earth's crust is not constant, but exhibits complicated fluctuations in speed amounting to several parts in 10(exp 8) [corresponding to a variation of several milliseconds (ms) in the Length Of the Day (LOD) and about one part in 10(exp 6) in the orientation of the rotation axis relative to the solid Earth's axis of figure (polar motion). These changes occur over a broad spectrum of time scales, ranging from hours to centuries and longer, reflecting the fact that they are produced by a wide variety of geophysical and astronomical processes. Geodetic observations of Earth rotation changes thus provide insights into the geophysical processes illustrated, which are often difficult to obtain by other means. In addition, these measurements are required for engineering purposes. Theoretical studies of Earth rotation variations are based on the application of Euler's dynamical equations to the problem of finding the response of slightly deformable solid Earth to variety of surface and internal stresses.

  10. Earth materials and earth dynamics

    SciTech Connect

    Bennett, K; Shankland, T.

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  11. On d+id Density Wave and Superconducting Orderings in Hole-Doped Cuprates

    NASA Astrophysics Data System (ADS)

    Goswami, Partha; Gahlot, Ajay Pratap Singh; Singh, Pankaj

    2013-05-01

    The d+id-density wave (chiral DDW) order, at the anti-ferromagnetic wave vector Q = (π, π), is assumed to represent the pseudo-gap (PG) state of a hole-doped cuprate superconductor. The pairing interaction U(k, k‧) required for d+id ordering comprises of (Ux2-y2(k, k‧), Uxy(k, k‧)), where Ux2-y2(k, k') = U1(cos kxa-cos kya)(cos k'xa- cos k'ya) and Uxy(k, k') = U2sin(kxa)sin(kya) sin(k'xa) sin(k'ya) with U1 > U2. The d-wave superconductivity (DSC), driven by an assumed attractive interaction of the form V(k, k') = -ěrt V1ěrt(cos kxa-cos kya)(cos k'xa- cos k'ya) where V1 is a model parameter, is discussed within the mean-field framework together with the d+id ordering. The single-particle excitation spectrum in the CDDW + DSC state is characterized by the Bogoluibov quasi-particle bands — a characteristic feature of SC state. The coupled gap equations are solved self-consistently together with the equation to determine the chemical potential (μ). With the pinning of the van Hove-singularities close to μ, one is able to calculate the thermodynamic and transport properties of the under-doped cuprates in a consistent manner. The electron specific heat displays non-Fermi liquid feature in the CDDW state. The CDDW and DSC are found to represent two competing orders as the former brings about a depletion of the spectral weight (and Raman response function density) available for pairing in the anti-nodal region of momentum space. It is also shown that the depletion of the spectral weight below Tc at energies larger than the gap amplitude occurs. This is an indication of the strong-coupling superconductivity in cuprates. The calculation of the ratio of the quasi-particle thermal conductivity αxx and temperature in the superconducting phase is found to be constant in the limit of near-zero quasi-particle scattering rate.

  12. Earth: Earth Science and Health

    NASA Technical Reports Server (NTRS)

    Maynard, Nancy G.

    2001-01-01

    A major new NASA initiative on environmental change and health has been established to promote the application of Earth science remote sensing data, information, observations, and technologies to issues of human health. NASA's Earth Sciences suite of Earth observing instruments are now providing improved observations science, data, and advanced technologies about the Earth's land, atmosphere, and oceans. These new space-based resources are being combined with other agency and university resources, data integration and fusion technologies, geographic information systems (GIS), and the spectrum of tools available from the public health community, making it possible to better understand how the environment and climate are linked to specific diseases, to improve outbreak prediction, and to minimize disease risk. This presentation is an overview of NASA's tools, capabilities, and research advances in this initiative.

  13. Inequivalence of Single-Particle and Population Lifetimes in a Cuprate Superconductor.

    PubMed

    Yang, S-L; Sobota, J A; Leuenberger, D; He, Y; Hashimoto, M; Lu, D H; Eisaki, H; Kirchmann, P S; Shen, Z-X

    2015-06-19

    We study optimally doped Bi-2212 (T(c)=96  K) using femtosecond time- and angle-resolved photoelectron spectroscopy. Energy-resolved population lifetimes are extracted and compared with single-particle lifetimes measured by equilibrium photoemission. The population lifetimes deviate from the single-particle lifetimes in the low excitation limit by 1-2 orders of magnitude. Fundamental considerations of electron scattering unveil that these two lifetimes are in general distinct, yet for systems with only electron-phonon scattering they should converge in the low-temperature, low-fluence limit. The qualitative disparity in our data, even in this limit, suggests that scattering channels beyond electron-phonon interactions play a significant role in the electron dynamics of cuprate superconductors. PMID:26196996

  14. Scattering rates and specific heat jumps in high-Tc cuprates

    NASA Astrophysics Data System (ADS)

    Storey, James

    Inspired by recent ARPES and tunneling studies on high-Tc cuprates, we examine the effect of a pair-breaking term in the self-energy on the shape of the electronic specific heat jump. It is found that the observed specific heat jump can be described in terms of a superconducting gap, that persists above the observed Tc, in the presence of a strongly temperature dependent pair-breaking scattering rate. An increase in the scattering rate is found to explain the non-BCS-like suppression of the specific heat jump with magnetic field. A discussion of these results in the context of other properties such as the superfluid density and Raman spectra will also be presented. Supported by the Marsden Fund Council from Government funding, administered by the Royal Society of New Zealand.

  15. Andreev nanoprobe of half-metallic CrO2 films using superconducting cuprate tips

    NASA Astrophysics Data System (ADS)

    Turel, C. S.; Guilaran, I. J.; Xiong, P.; Wei, J. Y. T.

    2011-11-01

    Superconducting tips of YBa2Cu3O7-x were used to perform point-contact Andreev reflection spectroscopy on half-metallic CrO2 thin films. At 4.2 K, strong suppression of the d-wave Andreev reflection characteristics was observed, consistent with the high spin polarization of CrO2. Our technique was validated by comparison with data taken on non-magnetic Au films and with data taken by superconducting Pb tips. The point contacts were estimated to be ≲10 nm in size, attesting to their ballistic and microscopic nature. Our results demonstrate the feasibility of using superconducting cuprate tips as spin-sensitive nanoprobes of ferromagnets.

  16. Thermal transport in the cuprates: Changes with doping across the phase diagram

    SciTech Connect

    Cohn, J.L.

    1996-12-31

    An overview of recent developments in the understanding of thermal conduction in the cuprates is presented. Anomalous phonon damping underlies an unusual temperature dependence of the in-plane thermal conductivity ({kappa}{sub ab}) for the insulating phases of some materials. This damping is sensitive to light oxygen doping in YBa{sub 2}Cu{sub 3}O{sub 6+x} (YBCO), is possibly related to local structural distortions, and may persist in superconducting compositions. New systematics for the superconducting-state enhancement of {kappa}{sub ab} are discussed. For YBCO the oxygen-doping dependence of the enhancement correlates with that of the pair density as determined by specific heat jumps. The large enhancements observed for fully-oxygenated specimens are attributed to pair condensation on the CuO chains. The implications of this finding and its possible connection with the emergence of the normal-state pseudogap are examined.

  17. Coexistence of Midgap Antiferromagnetic and Mott States in Undoped, Hole- and Electron-Doped Ambipolar Cuprates

    NASA Astrophysics Data System (ADS)

    Yin, Xinmao; Zeng, Shengwei; Das, Tanmoy; Baskaran, G.; Asmara, Teguh Citra; Santoso, Iman; Yu, Xiaojiang; Diao, Caozheng; Yang, Ping; Breese, Mark B. H.; Venkatesan, T.; Lin, Hsin; Ariando; Rusydi, Andrivo

    2016-05-01

    We report the first observation of the coexistence of a distinct midgap state and a Mott state in undoped and their evolution in electron and hole-doped ambipolar Y0.38 La0.62 (Ba0.82 La0.18 )2Cu3 Oy films using spectroscopic ellipsometry and x-ray absorption spectroscopies at the O K and Cu L3 ,2 edges. Supported by theoretical calculations, the midgap state is shown to originate from antiferromagnetic correlation. Surprisingly, while the magnetic state collapses and its correlation strength weakens with dopings, the Mott state in contrast moves toward a higher energy and its correlation strength increases. Our result provides important clues to the mechanism of electronic correlation strengths and superconductivity in cuprates.

  18. Fluctuating charge order in the cuprates: Spatial anisotropy and feedback from superconductivity

    NASA Astrophysics Data System (ADS)

    Wang, Yuxuan; Chowdhury, Debanjan; Chubukov, Andrey V.

    2015-10-01

    We analyze the form of static charge susceptibility χ (q ) in underdoped cuprates near axial momenta (Q ,0 ) and (0 ,Q ) at which short-range static charge order has been observed. We show that the momentum dependence of χ (q ) is anisotropic, and the correlation length in the longitudinal direction is larger than in the transverse direction. We show that correlation lengths in both directions decrease once the system evolves into a superconductor, as a result of the competition between superconductivity and charge order. These results are in agreement with resonant x-ray scattering data [R. Comin et al., Science 347, 1335 (2015), 10.1126/science.1258399]. We also argue that density and current components of the charge order parameter are affected differently by superconductivity: the charge density component is reduced less than the current component and hence extends deeper into the superconducting state. This gives rise to two distinct charge order transitions at zero temperature.

  19. Weak phase stiffness and nature of the quantum critical point in underdoped cuprates

    DOE PAGESBeta

    Yildirim, Yucel; Ku, Wei

    2015-11-02

    We demonstrate that the zero-temperature superconducting phase diagram of underdoped cuprates can be quantitatively understood in the strong binding limit, using only the experimental spectral function of the “normal” pseudogap phase without any free parameter. In the prototypical (La1–xSrx)2CuO4, a kinetics-driven d-wave superconductivity is obtained above the critical doping δc ~ 5.2%, below which complete loss of superfluidity results from local quantum fluctuation involving local p-wave pairs. Near the critical doping, an enormous mass enhancement of the local pairs is found responsible for the observed rapid decrease of phase stiffness. Lastly, a striking mass divergence is predicted at δc thatmore » dictates the occurrence of the observed quantum critical point and the abrupt suppression of the Nernst effects in the nearby region.« less

  20. Tunneling evidence of strong cooper-pair-breaking near T c in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Wolf, E. L.; Tao, H. J.; Susla, B.

    1991-02-01

    The superconductive tunneling density of states obtained from conventional metal film-insulator tunnel junctions on cleaved (ab) basal planes of single crystal Bi 2Sr 2CaCu 2O 8+y (2212) reveals a rising pair breaking rate Γ(T) near T c, as predicted by Lee and Read. We obtain Γ(T)=2.3 kT c(T/T c) 3, which confirms a recent calculation by Coffey and also recent tunneling results of Takada et al on YBa 2Cu 3O 6. This implies a pair lifetime at T c of about 40 fs in 2212. The results indicate that the T 3 pairbreaking near T c is an intrinsic feature of superconductivity in the cuprate planes.

  1. Electronic polymers and soft-matter-like broken symmetries in underdoped cuprates

    PubMed Central

    Capati, M.; Caprara, S.; Di Castro, C.; Grilli, M.; Seibold, G.; Lorenzana, J.

    2015-01-01

    Empirical evidence in heavy fermion, pnictide and other systems suggests that unconventional superconductivity appears associated to some form of real-space electronic order. For the cuprates, despite several proposals, the emergence of order in the phase diagram between the commensurate antiferromagnetic state and the superconducting state is not well understood. Here we show that in this regime doped holes assemble in ‘electronic polymers'. Within a Monte Carlo study, we find that in clean systems by lowering the temperature the polymer melt condenses first in a smectic state and then in a Wigner crystal both with the addition of inversion symmetry breaking. Disorder blurs the positional order leaving a robust inversion symmetry breaking and a nematic order, accompanied by vector chiral spin order and with the persistence of a thermodynamic transition. Such electronic phases, whose properties are reminiscent of soft-matter physics, produce charge and spin responses in good accord with experiments. PMID:26144868

  2. Doping Dependent Charge Transfer Gap and Realistic Electronic Model of n-type Cuprate Superconductors

    SciTech Connect

    Xiang, T.

    2010-05-03

    Based on the analysis of the measurement data of angle-resolved photoemission spectroscopy (ARPES) and optics, we show that the charge transfer gap is significantly smaller than the optical one and is reduced by doping in electron doped cuprate superconductors. This leads to a strong charge fluctuation between the Zhang-Rice singlet and the upper Hubbard bands. The basic model for describing this system is a hybridized two-band t-J model. In the symmetric limit where the corresponding intra- and inter-band hopping integrals are equal to each other, this two-band model is equivalent to the Hubbard model with an antiferromagnetic exchange interaction (i.e. the t-U-J model). The mean-field result of the t-U-J model gives a good account for the doping evolution of the Fermi surface and the staggered magnetization.

  3. Hall effect and Fermi surface reconstruction via electron pockets in the high-Tc cuprates

    NASA Astrophysics Data System (ADS)

    Storey, J. G.

    2016-01-01

    The mechanism by which the Fermi surface of high-T c cuprates undergoes a dramatic change from a large hole-like barrel to small arcs or pockets on entering the pseudogap phase remains a question of fundamental importance. Here we calculate the normal-state Hall coefficient from the resonating-valence-bond spin-liquid model developed by Yang, Rice and Zhang. In this model, reconstruction of the Fermi surface occurs via an intermediate regime where the Fermi surface consists of both hole- and electron-like pockets. We find that the doping (x) dependence of the Hall number transitions from 1+x to (x) over this narrow doping range. At low temperatures, a switch from a downturn to an upturn in the Hall coefficient signals the departure of the electron-like pockets from the Fermi surface.

  4. Tracking Cooper pairs in a cuprate superconductor by ultrafast angle-resolved photoemission.

    PubMed

    Smallwood, Christopher L; Hinton, James P; Jozwiak, Christopher; Zhang, Wentao; Koralek, Jake D; Eisaki, Hiroshi; Lee, Dung-Hai; Orenstein, Joseph; Lanzara, Alessandra

    2012-06-01

    In high-temperature superconductivity, the process that leads to the formation of Cooper pairs, the fundamental charge carriers in any superconductor, remains mysterious. We used a femtosecond laser pump pulse to perturb superconducting Bi(2)Sr(2)CaCu(2)O(8+δ) and studied subsequent dynamics using time- and angle-resolved photoemission and infrared reflectivity probes. Gap and quasiparticle population dynamics revealed marked dependencies on both excitation density and crystal momentum. Close to the d-wave nodes, the superconducting gap was sensitive to the pump intensity, and Cooper pairs recombined slowly. Far from the nodes, pumping affected the gap only weakly, and recombination processes were faster. These results demonstrate a new window into the dynamical processes that govern quasiparticle recombination and gap formation in cuprates. PMID:22654053

  5. Quasistatic magnetoelectric multipoles as order parameter for pseudogap phase in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Fechner, M.; Fierz, M. J. A.; Thöle, F.; Staub, U.; Spaldin, N. A.

    2016-05-01

    We introduce a mechanism in which coupling between fluctuating spin magnetic dipole moments and polar optical phonons leads to a nonzero ferroic ordering of quasistatic magnetoelectric multipoles. Using first-principles calculations within the LSDA +U method of density functional theory, we calculate the magnitude of the effect for the prototypical cuprate superconductor HgBa2CuO4 . We show that our proposed mechanism is consistent, to our knowledge, with all experimental data for the onset of the pseudogap phase and therefore propose the quasistatic magnetoelectric multipole as a possible pseudogap order parameter. Finally, we show that our mechanism embraces some key aspects of previous theoretical models, in particular the description of the pseudogap phase in terms of orbital currents.

  6. Physics of {pi}-meson condensation and high temperature cuprate superconductors

    SciTech Connect

    Sushkov, O. P.

    2009-08-15

    The idea of condensation of the Goldstone {pi}-meson field in nuclear matter had been put forward a long time ago. However, it was established that the normal nuclear density is too low, it is not sufficient to condensate {pi} mesons. This is why the {pi} condensation has never been observed. Recent experimental and theoretical studies of high-temperature cuprate superconductors have revealed condensation of Goldstone magnons, the effect fully analogous to the {pi} condensation. The magnon condensation has been observed. It is clear now that quantum fluctuations play a crucial role in the condensation, in particular they drive a quantum phase transition that destroys the condensate at some density of fermions.

  7. Formation of Gapless Fermi Arcs and Fingerprints of Order in the Pseudogap State of Cuprate Superconductors

    SciTech Connect

    Kondo, Takeshi; Palczewski, Ari D.; Hamaya, Yoichiro; Takeuchi, Tsunehiro; Wen, J. S.; Gu, Genda; Kaminski, Adam

    2013-10-11

    We use angle-resolved photoemission spectroscopy and a new quantitative approach based on the partial density of states to study properties of seemingly disconnected portions of the Fermi surface (FS) that are present in the pseudogap state of cuprates called Fermi arcs. We find that the normal state FS collapses very abruptly into Fermi arcs at the pseudogap temperature (T∗). Surprisingly, the length of the Fermi arcs remains constant over an extended temperature range between T∗ and Tpair, consistent with the presence of an ordered state below T∗. These arcs collapse again at the temperature below which pair formation occurs (Tpair) either to a point or a very short arc, whose length is limited by our experimental resolution. The tips of the arcs span between points defining a set of wave vectors in momentum space, which are the fingerprints of the ordered state that causes the pseudogap.

  8. Formation of Gapless Fermi Arcs and Fingerprints of Order in the Pseudogap State of Cuprate Superconductors

    SciTech Connect

    Kondo, Takeshi; Palczewski, Ari; Hamaya, Yoichiro; Takeuchi, Tsunehiro; Wen, J. S.; Xu, Z. J.; Gu, Genda; Kaminski, Adam

    2013-10-08

    We use angle-resolved photoemission spectroscopy and a new quantitative approach based on the partial density of states to study properties of seemingly disconnected portions of the Fermi surface (FS) that are present in the pseudogap state of cuprates called Fermi arcs. We find that the normal state FS collapses very abruptly into Fermi arcs at the pseudogap temperature (T*). Surprisingly, the length of the Fermi arcs remains constant over an extended temperature range between (T*) and Tpair, consistent with the presence of an ordered state below T*. These arcs collapse again at the temperature below which pair formation occurs (Tpair) either to a point or a very short arc, whose length is limited by our experimental resolution. The tips of the arcs span between points defining a set of wave vectors in momentum space, which are the fingerprints of the ordered state that causes the pseudogap.

  9. High-energy anomalies in covalent high-Tc cuprates with large Hubbard Ud on copper

    NASA Astrophysics Data System (ADS)

    Barišić, O. S.; Barišić, S.

    2015-03-01

    A large Ud theory is constructed for the metallic state of high-Tc cuprates. The Emery three-band model, extended with Ox-Oy hopping tpp, and with Ud → ∞, is mapped on slave fermions. The Dyson time-dependent diagrammatic theory in terms of the Cu-O hopping tpd, starting from the nondegenerate unperturbed ground state, is translationally and asymptotically locally gauge invariant. The small parameter of the theory is the average hole occupation of Cu sites nd. The lowest order of the theory generates the single particle propagators of the hybridized pdp- and dpd-fermions with the exact covalent three band structure. The leading many-body effect is band narrowing, accompanied by Landau-like damping of the single particle propagation, due to incoherent local charge Cu-O fluctuations. The corresponding continuum is found below and above the Fermi level.

  10. Role of Lattice Coupling in Establishing Electronic and Magnetic Properties in Quasi-One-Dimensional Cuprates

    NASA Astrophysics Data System (ADS)

    Lee, W. S.; Johnston, S.; Moritz, B.; Lee, J.; Yi, M.; Zhou, K. J.; Schmitt, T.; Patthey, L.; Strocov, V.; Kudo, K.; Koike, Y.; van den Brink, J.; Devereaux, T. P.; Shen, Z. X.

    2013-06-01

    High resolution resonant inelastic x-ray scattering has been performed to reveal the role of lattice coupling in a family of quasi-1D insulating cuprates, Ca2+5xY2-5xCu5O10. Site-dependent low-energy excitations arising from progressive emissions of a 70 meV lattice vibrational mode are resolved for the first time, providing a direct measurement of electron-lattice coupling strength. We show that such electron-lattice coupling causes doping-dependent distortions of the Cu-O-Cu bond angle, which sets the intrachain spin exchange interactions. Our results indicate that the lattice degrees of freedom are fully integrated into the electronic behavior in low-dimensional systems.