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Cuprate Superconductors (cuprate + superconductor)
Selected AbstractsInterplay of magnetism and superconductivityPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006M. Akhavan Abstract After about two decades of intense research since the discovery of high-temperature superconductivity (HTSC) in cuprates, although many aspects of the physics and chemistry of these cuprate superconductors are now well understood, the underlying pairing mechanism remains elusive. Magnetism and superconductivity are usually thought as incompatible, but in number of special materials including HTSCs these two mutually excluding mechanisms are found to coexist. The presence in a system of superconductivity and magnetism, gives rise to a large number of interesting phenomenon. This article provides perspective on recent developments and their implications for our understanding of the interplay between magnetism and superconductivity in new materials. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Forward scattering peak in the electron,phonon interaction and impurity scattering of cuprate superconductorsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2005M. L. Kuli Abstract The important role of the electron,phonon interaction (EPI) in explaining the normal state properties and pairing mechanism in high- Tc superconductors (HTSC) is discussed. A number of experiments are analyzed such as: dynamical conductivity, Raman scattering, neutron scattering, ARPES, tunnelling measurements, and etc. They give convincing evidence that the EPI dominantly contributes to pairing in HTSC oxides. Strong electronic correlations cause the forward scattering peak (FSP) in the EPI and in the non-magnetic impurity potential. The theory based on the FSP (whatever is its origin) explains several puzzling experimental results in ARPES and transport: (1) much smaller transport coupling constant than the pairing one (,tr , ,ph); (2) the ARPES non-shift puzzle , where the nodal kink at 70 meV is unshifted in the superconducting state while the anti-nodal one at 40 meV is shifted; (3) d-wave superconductivity due to the EPI; (4) robustness of d-wave pairing in the presence of nonmagnetic impurities; (5) collapse of the elastic scattering rate near the anti-nodal point in the superconducting state; (6) anomalous temperature dependence of the Hall angle in optimally doped HTSC. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Apical oxygen, 3D-2D cross over and superconductivity in Sm2,xCexCuO4,,PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2006M. Boujida Abstract In spite of the vast amount of experimental and theoretical articles accumulated in HTSC, the mechanism of the interaction driving charge carriers to form Cooper pairs below Tc is still unknown. The comparison of the normal state transport properties of YBa2Cu3O7,, and the Sm2,xCexCuO4,, [1, 2] might shed some light on the microscopic origin of HTSC. In comparison to the YBCO, the apical oxygen in Sm2,xCexCuO4,, [3] destroys the superconductivity via the vertical ionic bonding which localizes the charge in the Cu-O squares, however the hole transfer by moving O(4) towards the CuO2 planes, leads to the optimization of YBCO properties. The behaviour of C axis parameter vs the oxygen content cannot be explained by a BSC mechanism. The high amount of anisotropy ratio [4] is explained by the sheer square planes in NCCO system, i.e. without apical oxygen (SC with Tc maximum). From the data of the resistivity in the normal state, we conclude the observation of a 3D-2D cross over only in Sm2,xCexCuO4,, [2] and Nd2,xCexCuO4,, [5] which is also related to its high anisotropy. The competition between anisotropy and superconductivity destroys the superconducting state in the 2D limit even in the ground state. In this material the superconductivity cannot be enhanced at high temperature because the compound is a quasi 2D system (sheer square planes of CuO2) and the cuprate superconductors is a genuine three-dimensional (3D) phenomenon [6]. The Josephson coupling between the different layers is S-I-S for NCCO and S-N-S for YBCO, thus the Lawrence and Doniach model (LD) [7] with neighbouring layers coupled by the Josephson tunnelling is appropriate. In summary the behaviour of apical oxygen is intrinsically different in the two kinds of cuprates. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Review of polyhedral distortions as a multi-scale minimization of the electric polarization and their correlations with physical propertiesACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2006Abderrahim Benabbas The Jahn,Teller (JT) and non-Jahn,Teller polyhedral distortions are reviewed within the same context, based on a multi-scale minimization of the electric polarization by handling formal ionic valences and valence electron density. This model is applied to tetragonal distortions of octahedra, particularly in K2NiF4 structures with different formula types, along with doping. The predictions are always in good agreement with the observed data. In particular, the ferrodistortive order of JT distortions is obtained from formal charge polarizations, while the antiferrodistortive one is adopted when only the valence electron density is involved. The correlations between physical properties and octahedral elongations through the crystal structures on one side and chemical compositions on the other side are discussed according to this model for high- Tc cuprate superconductors and CMR manganites. [source] Drude behavior in the far-infrared conductivity of cuprate superconductors ,ANNALEN DER PHYSIK, Issue 7-8 2006H.L. Liu Abstract When viewed at frequencies below about 8 THz (250 cm -1; 30 meV) the ab -plane optical conductivity of the cuprate superconductors (in their normal state) is well described by a Drude model. Examples include optimally-doped YBa2Cu3O7-, and Bi2Sr2CaCu2O8; even the underdoped phases have a Drude character to their optical conductivity. A residual Drude-like normal fluid is seen in the superconducting state in most cases; the scattering rate of this quasiparticle contribution collapses at Tc. [source] Making the transition temperature of cuprate superconductors higher by using the field-effect-transistor geometryANNALEN DER PHYSIK, Issue 1-2 2004M. Hayashi Abstract We present a possibility to raise the transition temperature of cuprate superconductors by using the field-effect-transistor type devices. The basic mechanism is based on the proximity effect of the two off-diagonal-long-range-orders in the superconducting phase of the cuprates, namely, the singlet resonating-valence-bond order and the bose condensation. Our model is based on the mean field theory of the t - J model. [source] | ||||||||||