Charge Localization from Local Destruction of Antiferromagnetic Correlation in Zn-doped YBa2Cu3O7-d

The in-plane normal-state resistivity of Zn-doped YBa2Cu3O7-d single crystals is measured down to low temperatures by suppressing superconductivity with magnetic fields up to 18 T. Substitution of Cu with Zn in the CuO2 planes is found to induce carrier localization at low temperatures in "clean" samples with kF l > 5, where the mean free path l is larger than the electron wave length and thus localization is not normally expected. The destruction of the local antiferromagnetic correlation among Cu spins by Zn is discussed to be the possible origin of this unusual charge localization.Comment: 4 pages of LaTeX (revtex and epsf) including 4 postscript figure

Zn-doping effect on the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta} single crystals

We report the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}Cu_{1-z}Zn_{z}O_{6+\delta} (Zn-doped BSLCO) single crystals with z of up to 2.2%. Besides the typical Zn-doping effects on the in-plane resistivity and the Hall angle, we demonstrate that the nature of the low-temperature normal state in the Zn-doped samples is significantly altered from that in the pristine samples under high magnetic fields. In particular, we observe nearly-isotropic negative magnetoresistance as well as an increase in the Hall coefficient at very low temperatures in non-superconducting Zn-doped samples, which we propose to be caused by the Kondo scattering from the local moments induced by Zn impurities.Comment: 4 pages, 4 figures, final version (one reference added), published in Phys. Rev.

Multi-layer scintillation detector for the MOON double beta decay experiment: Scintillation photon responses studied by a prototype detector MOON-1

An ensemble of multi-layer scintillators is discussed as an option of the high-sensitivity detector Mo Observatory Of Neutrinos (MOON) for spectroscopic measurements of neutrino-less double beta decays. A prototype detector MOON-1, which consists of 6 layer plastic-scintillator plates, was built to study the sensitivity of the MOON-type detector. The scintillation photon collection and the energy resolution, which are key elements for the high-sensitivity experiments, are found to be 1835+/-30 photo-electrons for 976 keV electrons and sigma = 2.9+/-0.1% (dE/E = 6.8+/-0.3 % in FWHM) at the Qbb ~ 3 MeV region, respectively. The multi-layer plastic-scintillator structure with good energy resolution as well as good background suppression of beta-gamma rays is crucial for the MOON-type detector to achieve the inverted hierarchy neutrino mass sensitivity.Comment: 8 pages, 16 figures, submitted to Nucl.Instrum.Met

Model of C-Axis Resistivity of High-\Tc Cuprates

We propose a simple model which accounts for the major features and systematics of experiments on the $c$-axis resistivity, $\rho_c$, for \lsco, \ybco and \bsco . We argue that the $c$-axis resistivity can be separated into contributions from in-plane dephasing and the $c$-axis ``barrier'' scattering processes, with the low temperature semiconductor-like behavior of $\rho_c$ arising from the suppression of the in-plane density of states measured by in-plane magnetic Knight shift experiments. We report on predictions for $\rho_c$ in impurity-doped \ybco materials.Comment: 10 pages + figures, also see March Meeting J13.1

Theory of Electric Transport in the Pseudogap State of High-Tc Cuprates

We theoretically investigate the electric transport in the pseudogap state of High-Tc cuprates. Starting from the repulsive Hubbard model, we perform the microscopic calculation to describe the pseudogap phenomena which are induced by the superconducting fluctuations. The single particle Green function, spin susceptibility and superconducting fluctuations are self-consistently determined by the SC-FLEX+T-matrix approximation. The longitudinal and transverse conductivities are calculated by using the Eliashberg and Kohno-Yamada formalism. The effects of the spin fluctuations and superconducting fluctuations are estimated, respectively. The vertex corrections arising from the two fluctuations are also calculated. The additional contribution from the Aslamazov-Larkin term is also estimated beyond the Eliashberg formalism. It is shown that the main effect of the superconducting fluctuations is the feedback effect through the spin fluctuations. The correct results are obtained by considering the superconducting fluctuations and the spin fluctuations simultaneously. The temperature and doping dependences of the resistivity and the Hall coefficient are well explained. We point out that the characteristic momentum dependence of the systems plays an essential role in this explanation.Comment: To appear in J. Phys. Soc. Jpn. Vol.71 No.1 (2002

Pseudogap and Superconducting Fluctuation in High-Tc Cuprates: Theory beyond 1-loop Approximation

The pseudogap phenomena induced by the SC fluctuation are investigated in details. We perform a calculation beyond the 1-loop approximation. The SC fluctuation is microscopically derived on the basis of the repulsive Hubbard model. The vertex corrections are collected in the infinite order with use of the quasi-static approximation. The single-particle excitations, NMR 1/T_{1}T, spin susceptibility and superconducting transition temperature are discussed. The important role of the vertex correction is pointed out for the single particle spectral function. On the other hand, the validity of the 1-loop order theory is confirmed for other quantities. We shed light on the essential nature of SC fluctuation leading to the pseudogap from the comparison with spin and charge fluctuations

TcT_c suppression in co-doped striped cuprates

We propose a model that explains the reduction of $T_c$ due to the pinning of stripes by planar impurity co-doping in cuprates. A geometrical argument about the planar fraction of carriers affected by stripe pinning leads to a a linear $T_c$ suppression as a function of impurity concentration $z$. The critical value $z_c$ for the vanishing of superconductivity is shown to scale like $T_c^2$ in the under-doped regime and becomes universal in the optimally- and over-doped regimes. Our theory agrees very well with the experimental data in single- and bi-layer cuprates co-doped with Zn, Li, Co, etc...Comment: 4 pages, 4 figure

Critical temperature of an anisotropic superconductor containing both nonmagnetic and magnetic impurities

The combined effect of both nonmagnetic and magnetic impurities on the superconducting transition temperature is studied theoretically within the BCS model. An expression for the critical temperature as a function of potential and spin-flip scattering rates is derived for a two-dimensional superconductor with arbitrary in-plane anisotropy of the superconducting order parameter, ranging from isotropic s-wave to d-wave (or any pairing state with nonzero angular momentum) and including anisotropic s-wave and mixed (d+s)-wave as particular cases. This expression generalizes the well-known Abrikosov-Gor'kov formula for the critical temperature of impure superconductors. The effect of defects and impurities in high temperature superconductors is discussed.Comment: 4 eps figure

Changes in mechanical properties of poly-l-lactic acid mini-plate under functional load simulating sagittal splitting ramus osteotomy

博士（歯学）・第1695号（甲第982号）・平成19年3月31