A. Matsuda

BCS-like Bogoliubov quasiparticles in high-T(c) superconductors observed by angle-resolved photoemission spectroscopy.

We performed high-resolution angle-resolved photoemission spectroscopy on triple-layered high-T(c) cuprate Bi(2)Sr(2)Ca(2)Cu(3)O(10+delta). We have observed the full energy dispersion (electron and hole branches) of Bogoliubov quasiparticles and determined the coherence factors above and below E(F) as a function of momentum from the spectral intensity as well as from the energy dispersion based on BCS theory. The good quantitative agreement between the experiment and the theoretical prediction suggests the basic validity of BCS formalism in describing the superconducting state of cuprates.

Doping dependence of anisotropic resistivities in the trilayered superconductor (formula presented)

The doping dependence of the themopower, in-plane resistivity rho_ab(T), out-of-plane resistivity rho_c(T), and susceptibility has been systematically measured for high-quality single crystal Bi2Sr2Ca2Cu3O10+delta. We found that the transition temperature Tc and pseudogap formation temperature T_rho_c*, below which rho_c shows a typical upturn, do not change from their optimum values in the overdoped region, even though doping actually proceeds. This suggests that, in overdoped region, the bulk

In-plane anisotropy on the transport properties in the modulated Bi2O2-based conductors Bi-2212 and Bi–Sr–Co–O

T_c

Structural Study of Inhomogeneous Charge Distribution of Inequivalent CuO2 Planes in Bi2.1Sr1.9Ca2Cu3O10+δ Single Crystals

is determined by the always underdoped inner plane, which have a large superconducting gap, while the carriers are mostly doped in the outer planes, which have a large phase stiffness.

Pseudogap in Bi2Sr2CaCu2O8+δ studied by measuring anisotropic susceptibilities and out-of-plane transport

Abstract We investigated the in-plane anisotropy on the resistivity and thermopower of the Bi2Sr2CaCu2O8+δ (Bi-2212) and Bi–Sr–Co–O (BiCo) single crystals. In Bi-2212, the b-axis resistivity is higher than the a-axis resistivity, and is expressed as a sum of the a-axis resistivity and an additional residual resistivity. A downward deviation due to pseudogap is observed below a characteristic temperature T ∗ which is isotropic in the form of conductivity. These results suggest that the modulation structure along the b-axis works as an anisotropic scattering center, but does not affect the pseudogap formation. On the other hand, the anisotropy of the resistivity and the thermopower in Pb-doped BiCo is substantial, probably owing to the misfit structure between the hexagonal CoO2 layer and the rock-salt Bi2O2 layer. However, the anisotropy in the resistivity in Pb-free BiCo is very small, suggesting that the inplane anisotropy is averaged by the modulation structure, whose direction is tilted by 45° from the a- and b-axis.

Direct evidence for superconducting quasiparticle in triple-layered high-Tc superconductor

Four-circle x-ray diffraction measurements were carried out on a single crystal of Bi 2.1 Sr 1.9 Ca 2 Cu 3 O 10+δ with doping levels from underdoped to overdoped. The excess charge of each inequivalent CuO 2 plane was estimated using the obtained inter-atomic distances in two ways by means of the bond–valence-sum method. The copper valence and the valence sum of the copper and the surrounding oxygen ions gave contradictory results for the inhomogeneous charge distribution of the inequivalent CuO 2 planes.

Low Energy Excitation and Scaling in [Formula presented] [Formula presented]: Angle-Resolved Photoemission Spectroscopy

Abstract We find in the Bi 2 Sr 2 CaCu 2 O 8+δ system that the characteristic temperatures T * χ (below which the uniform susceptibilities χ ab ( T ) ( H ⊥ c ) and χ c ( T ) ( H ‖ c ) decrease) and T * ϱ c (below which the out-of-plane resistivity ϱ c ( T ) shows typical upturn) coincidence for all doping levels. We attribute the T dependence of χs and ϱ c to the anomalous (pseudogapped) density-of-states (DOS) in high- T c cuprates. In addition, an analysis of the anisotropy in the T dependence of χs shows that the high-temperature component ( d χ/ dT

Quasiparticles and Energy Scaling in Bi

We have performed angle-resolved photoemission spectroscopy (ARPES) on triple-layered high-T-c cuprate superconductor Bi2Sr2Ca2Cu3O10+delta. We found a direct experimental evidence for Bogoliubov quasiparticle in high-T-c cuprates by observing the full energy dispersion below and above the Fermi level. The excellent quantitative agreement in the dispersion as well as the coherence factors between the ARPES experiment and Bardeen, Cooper and Shrieffer (BCS) theory establishes the validity and universality of the basic framework of BCS theory in high-T-c cuprates

_2

Angle-resolved photoemission spectroscopy (ARPES) has been performed on the single- to triple-layered Bi-family high-T (c) superconductors (Bi(2)Sr(2)Ca(n-1)Cu(n)O(2n+4), n=1-3). We found a sharp coherent peak as well as a pseudogap at the Fermi level in the triple-layered compound. Comparison among three compounds has revealed a universal rule that the characteristic energies of superconducting and pseudogap behaviors are scaled with the maximum T (c).

Sr

Angle-resolved photoemission spectroscopy (ARPES) has been performed on the single- to triple-layered Bi-family high-T (c) superconductors (Bi(2)Sr(2)Ca(n-1)Cu(n)O(2n+4), n=1-3). We found a sharp coherent peak as well as a pseudogap at the Fermi level in the triple-layered compound. Comparison among three compounds has revealed a universal rule that the characteristic energies of superconducting and pseudogap behaviors are scaled with the maximum T (c).