Publications (14)22.76 Total impact
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Article: Low-frequency structural dynamics in the incommensurate composite crystal Bi2Sr2CuO6 + δ
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ABSTRACT: Inelastic coherent neutron scattering experiments have been performed to study the low-frequency structural excitations in single crystals of the incommensurate superconducting Bi2Sr2CuO6 + δ (Bi-2201) system. As in the Bi-2212 family, the observation of two well-defined propagating "acoustic-like" branches around the main Bragg reflections reflects its composite nature. The two modes naturally correspond to the separate motions of the two sublattices. Constant-Q scans reveal a rapid evolution of the dynamical structure factor with the wave vector.EPL (Europhysics Letters) 01/2007; 66(2):246. · 2.17 Impact Factor -
Article: Acoustic phonons in the aperiodic layered crystal of Bi2Sr2CaCu2O8 + δ
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ABSTRACT: We present neutron scattering investigations of the structural dynamical properties of the aperiodic layered compound, Bi2Sr2CaCu2O8 + δ. Acoustic phonons behave identically around the assumed average structure Bragg reflection and around the first satellite. This observation proves that the collective dynamics related to the incommensurate structure are quite different from what is expected in a modulated incommensurate model. Our data indicate two acoustic-like longitudinal branches along the incommensurate direction. Such behavior is compatible with a composite incommensurate structure where these two Bragg peaks correspond to the main reflections of each subsystem.EPL (Europhysics Letters) 01/2007; 55(2):201. · 2.17 Impact Factor -
Article: Odd and even magnetic resonant modes in highly overdoped Bi_2 Sr_2 Ca Cu_2 O_{8+delta}
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ABSTRACT: We present inelastic neutron scattering data on highly overdoped Bi_2 Sr_2 Ca Cu_2 O_{8+\delta} single crystals with superconducting transition temperature T_C=70 K and, for comparison, a nearly optimally doped crystal with T_C=87 K. In both samples, magnetic resonant modes with odd and even symmetry under exchange of the two CuO_2 layers in the unit cell are observed. In the overdoped sample, the linewidth of the odd mode is reduced compared with the optimally doped sample. This finding is discussed in conjunction with recent evidence for intrinsic inhomogeneities in this compound. The data on odd and even resonant excitations are otherwise fully consistent with trends established on the basis of data on YBa_2Cu_3O_{6+x}. This confirms the universality of these findings and extends them into the highly overdoped regime of the phase diagram.12/2006; -
Article: Phase evolution, structural and superconducting properties of Pb-free Bi2Sr2Ca2Cu3O10+δ single crystals
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ABSTRACT: Sizable Bi2Sr2Ca2Cu3O10+δ (Bi-2223) single crystals were grown by the travelling solvent floating zone technique and subsequently annealed in O2 and/or Ar flow for 120–500 h in a temperature range of 430–850 °C. The effect of annealing on the phase evolution as well as the structural and superconducting properties was studied using x-ray diffraction (XRD) and magnetization measurements as well as ellipsometric measurements of the far-infrared c-axis conductivity. The results show that some of the as-grown Bi-2223 crystals are nearly phase pure, while others contain a certain amount of Bi2Sr2CaCu2O8+δ (Bi-2212), Ca2CuO3 and CuO phases co-existing with the Bi-2223 phase. Annealing these multi-phase crystals in O2 flow at high temperature can lead to a phase transformation from Bi-2212 to Bi-2223, which can be understood by a layer-intercalation mechanism. For the samples consisting of Bi-2212 phase, nearly phase-pure Bi-2223 crystals can be obtained by high-temperature, long-time annealing. Annealing phase-pure crystals in various atmospheres, temperatures and pressures (ranging from 1 to 550 bar) causes an alteration in oxygen content, resulting in a systematic change in the c-axis lattice parameters and superconducting transition temperature Tc. Interestingly, Tc is found to increase with decreasing c-axis lattice parameters reaching K, but change very little with the further decrease of c-axis lattice parameters, exhibiting a broad plateau on the plot of Tc versus c-axis lattice constant. The magnetization and ellipsometric measurements on high-oxygen-pressure annealed Bi-2223 crystals show much stronger Josephson coupling between the CuO2 layers, indicating a progressively higher hole doping upon increasing annealing oxygen pressure, although Tc remains essentially unchanged. The anomalous saturation of Tc on the overdoped side is quite unique compared with the mono- or bi-layered Bi-based cuprates. It is possibly related to the significant difference in the hole doping between the crystallographically inequivalent inner and outer CuO2 planes in the multi-layered cuprate system.Superconductor Science and Technology 03/2004; 17(6):731. · 2.66 Impact Factor -
Article: Two resonant magnetic modes in an overdoped high T_c superconductor.
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ABSTRACT: A detailed inelastic neutron scattering study of the overdoped high temperature copper oxide superconductor Y(0.9)Ca(0.1)Ba(2)Cu(3)O(7) reveals two-distinct magnetic resonant modes in the superconducting state. The modes differ in their symmetry with respect to exchange between adjacent copper oxide layers. Counterparts of the mode with odd symmetry, but not the one with even symmetry, had been observed before at lower doping levels. The observation of the even mode resolves a long-standing puzzle, and the spectral weight ratio of both modes yields an estimate of the onset of particle-hole spin-flip excitations.PRL. 01/2004; 91(23):237002. -
Article: Two Resonant Magnetic Modes in an Overdoped High Tc Superconductor
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ABSTRACT: A deta iled inelastic neutron scattering study of the overdoped high temperature copper oxide superconductor Y0:9Ca0:1Ba2Cu3O7 reveals two-distinct magnetic resonant modes i n the superconducting state. T he modes differ in their symmetry with respect to exchange between adjacent copper oxide layers. Counter parts of the mode with odd symmetry, but not the one with even symmetry, had been observed before at lower doping levels. The observation of the even mode resolves a long-standing puzzle, and the spectral weight ratio of both modes yields an estimate of the onset of par icle - hole spin-flip excit at ions.Physical Review Letters 12/2003; 91(23):237002. · 7.37 Impact Factor -
Article: Two resonant magnetic modes in an overdoped high-$\bf T_c$ superconductor
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ABSTRACT: A detailed inelastic neutron scattering study of the overdoped high temperature copper oxide superconductor ${Y_{0.9}Ca_{0.1}Ba_{2}Cu_3O_{7}}$ reveals two distinct magnetic resonant modes in the superconducting state. The modes differ in their symmetry with respect to exchange between adjacent copper oxide layers. Counterparts of the mode with odd symmetry, but not the one with even symmetry, had been observed before at lower doping levels. The observation of the even mode resolves a long-standing puzzle, and the spectral weight ratio of both modes yields an estimate of the onset of particle-hole spin-flip excitations.09/2003; -
Article: C-axis lattice dynamics in Bi-based cuprate superconductors
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ABSTRACT: We present results of a systematic study of the c axis lattice dynamics in single layer Bi2Sr2CuO6 (Bi2201), bilayer Bi2Sr2CaCu2O8 (Bi2212) and trilayer Bi2Sr2Ca2Cu3O10 (Bi2223) cuprate superconductors. Our study is based on both experimental data obtained by spectral ellipsometry on single crystals and theoretical calculations. The calculations are carried out within the framework of a classical shell model, which includes long-range Coulomb interactions and short-range interactions of the Buckingham form in a system of polarizable ions. Using the same set of the shell model parameters for Bi2201, Bi2212 and Bi2223, we calculate the frequencies of the Brillouin-zone center phonon modes of A2u symmetry and suggest the phonon mode eigenvector patterns. We achieve good agreement between the calculated A2u eigenfrequencies and the experimental values of the c axis TO phonon frequencies which allows us to make a reliable phonon mode assignment for all three Bi-based cuprate superconductors. We also present the results of our shell model calculations for the Gamma-point A1g symmetry modes in Bi2201, Bi2212 and Bi2223 and suggest an assignment that is based on the published experimental Raman spectra. The superconductivity-induced phonon anomalies recently observed in the c axis infrared and resonant Raman scattering spectra in trilayer Bi2223 are consistently explained with the suggested assignment. Comment: 29 pages, 13 figures07/2003; -
Article: Josephson plasma resonance and phonon anomalies in trilayer Bi2Sr2Ca2Cu3O10.
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ABSTRACT: The far-infrared (FIR) c axis conductivity of a Bi2223 crystal has been measured by ellipsometry. Below T(c) a strong absorption band develops near 500 cm(-1), corresponding to a transverse Josephson plasmon. The related increase in FIR spectral weight leads to a giant violation of the Ferrell-Glover-Tinkham sum rule. The gain in c axis kinetic energy accounts for a sizable part of the condensation energy. We also observe phonon anomalies which suggest that the Josephson currents lead to a drastic variation of the local electric field within the block of closely spaced CuO2 planes.Physical Review Letters 01/2003; 89(27):277001. · 7.37 Impact Factor -
Article: Josephson plasma resonance and phonon anomalies in trilayer Bi_2Sr_2Ca_2Cu_3O_10 superconductor
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ABSTRACT: The far-infrared (FIR) c axis conductivity of a Bi2223 crystal has been measured by ellipsometry. Below T$_c$ a strong absorption band develops near 500 cm $^{-1}$, corresponding to a transverse Josephson-plasmon. The related increase in FIR spectral weight leads to a giant violation of the Ferrell-Glover-Tinkham sum-rule. The gain in c axis kinetic energy accounts for a sizeable part of the condensation energy. We also observe phonon anomalies which suggest that the Josephson-currents lead to a drastic variation of the local electric field within the block of closely spaced CuO$_2$ planes. Comment: 8 pages, 3 figures05/2002; -
Article: Resonant spin excitation in an overdoped high temperature superconductor.
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ABSTRACT: An inelastic neutron scattering study of overdoped Bi(2)Sr(2)CaCu(2)O(8+delta) ( T(c) = 83 K) has revealed a resonant spin excitation in the superconducting state. The mode energy is E(res) = 38.0 meV, significantly lower than in optimally doped Bi(2)Sr(2)CaCu(2)O(8+delta) ( T(c) = 91 K, E(res) = 42.4 meV). This observation, which indicates a constant ratio E(res)/k(B)T(c) approximately 5.4, helps resolve a long-standing controversy about the origin of the resonant spin excitation in high temperature superconductors.PRL. 03/2001; 86(8):1610-3. -
Article: Spin Excitations in Cuprates: From Underdoped to Overdoped State
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ABSTRACT: We review recent results of neutron scattering studies of the YBa2 Cu306+z and Bi2 Sr2 CaCu20s+~ high temper-ature superconductors, with a focus on the magnetic resonance peak that dominates the spin excitation spectrum in these two compounds.Physica C Superconductivity 01/2000; 341:348. · 1.01 Impact Factor -
Article: Odd and even magnetic resonant modes in highly overdoped Bi_ {2} Sr_ {2} CaCu_ {2} O_ {8+ δ}
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ABSTRACT: We present inelastic neutron scattering data on highly overdoped Bi2Sr2CaCu2O8+δ single crystals with superconducting transition temperature TC=70 K and, for comparison, a nearly optimally doped crystal with TC=87 K. In both samples, magnetic resonant modes with odd and even symmetry under exchange of the two CuO2 layers in the unit cell are observed. In the overdoped sample, the linewidth of the odd mode is reduced compared with the optimally doped sample. This finding is discussed in conjunction with recent evidence for intrinsic inhomogeneities in this compound. The data on odd and even resonant excitations are otherwise fully consistent with trends established on the basis of data on YBa2Cu3O6+x. This confirms the universality of these findings and extends them into the highly overdoped regime of the phase diagram.Phys. Rev. B. 75(6). -
Article: Odd and even magnetic resonant modes in highly overdoped Bi2 Sr2 Ca Cu2 O8+δ
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ABSTRACT: Cited By (since 1996): 17, Export Date: 4 March 2012, Source: Scopus, Art. No.: 060502, CODEN: PRBMD, doi: 10.1103/PhysRevB.75.060502, Language of Original Document: English, Correspondence Address: Capogna, L.; INFM-CNR SOFT, OGG, 6 Rue J. Horowitz, 38042 Grenoble Cedex 9, France; email: capogna@ill.fr, References: Eschrig, M., (2006) Adv. Phys., 55, p. 47. , For a review, see ADPHAH 0001-8732 10.1080/00018730600645636;Physical Review B - Condensed Matter and Materials Physics. 75(6).
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Institutions
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2001–2007
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Max-Planck-Institut für Festkörperforschung
Stuttgart, Baden-Wuerttemberg, Germany
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