Shintaro Adachi

Doping dependencies of onset temperatures for the pseudogap and superconductive fluctuation in Bi2Sr2CaCu2O8+δ, studied from both in-plane and out-of-plane magnetoresistance measurements

To investigate the relationship between the pseudogap and superconductivity, we measured both the in-plane (ρab) and out-of-plane (ρc) resistivity for oxygen-controlled Bi2Sr2CaCu2O8+δ single crystals subject to magnetic fields (parallel to the c-axis) of up to 17.5 T. The onset temperature for the superconductive fluctuation, Tscf, is determined by the large positive in-plane magnetoresistance (MR) and negative out-of-plane MR observed near Tc, whereas the pseudogap opening temperature T* is determined by the semiconductive upturn of the zero-field ρc. Tscf was found to scale roughly as Tc, with a decreasing temperature interval between them upon doping. On the other hand, T* starts out much higher than Tscf but decreases monotonically upon doping; finally, at a heavily overdoped state, it is not observed above Tscf. These results imply that the pseudogap is not a simple precursor of superconductivity, but that further study is needed to determine whether or not T* exists below Tscf in the heavily overdo...

Observation of Bogoliubov Band Hybridization in the Optimally Doped Trilayer Bi2Sr2Ca2Cu3O10+δ

Using a laser-excited angle-resolved photoemission spectroscopy capable of bulk sensitive and high-energy resolution measurements, we reveal a new phenomenon of superconductors in the optimally doped trilayer Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{10+δ}. We observe a hybridization of the Bogoliubov bands derived from the inner and outer CuO_{2} planes with different magnitudes of energy gaps. Our data clearly exhibit the splitting of coherent peaks and the consequent enhancement of spectral gaps. These features are reproduced by model calculations, which indicate that the gap enhancement extends over a wide range of Fermi surface up to the antinode. The significant modulation of electron pairing uncovered here might be a crucial factor to achieve the highest critical temperature in the trilayer cuprates.

Origin of positive out-of-plane magnetoconductivity in overdoped Bi

To elucidate the pseudogap phase diagram including the overdoped state of high transition temperature (high-

_{1.6}

T_c

Pb

) cuprates, we must understand the origin of the positive out-of-plane magnetoconductivity (MC) observed in these compounds. For this purpose, the out-of-plane resistivity

_{0.4}

\rho_c(T,H)

Sr

of an overdoped Bi

_{2}

_{1.6}

CaCu

Pb

_{1.96}

_{0.4}