Mott transition in cuprate high-temperature superconductors

In this study, we investigate the metal-insulator transition of charge transfer type in high-temperature cuprates. We first show that we must introduce a new band parameter in the three-band d-p model to reproduce the Fermi surface of high temperature cuprates such as BSCCO, YBCO and Hg1201. We present a new wave function of a Mott insulator based on the improved Gutzwiller function, and show that there is a transition from a metal to a charge-transfer insulator for such parameters by using the variational Monte Carlo method. This transition occurs when the level difference $\Delta_{dp}\equiv \epsilon_p-\epsilon_d$ between d and p orbitals reaches a critical value $(\Delta_{dp})_c$. The energy gain $\Delta E$, measured from the limit of large $\Delta_{dp}$, is proportional to $1/\Delta_{dp}$ for $\Delta_{dp}>(\Delta_{dp})_c$: $\Delta E\propto -t_{dp}^2/\Delta_{dp}$. We obtain $(\Delta_{dp})_c\simeq 2t_{dp}$ using the realistic band parameters

The diversity of Asia and the future of Asian integration

Content: 1)The economic development of Asia and extension of its political influence in the world. 2)The present state and the future of Asian economic and political integration. 3)Cultural diversity and disparity in economic development in Asia. 4)The future role of Asia in the worl

SOVEREIGNTY VS INTERNATIONAL COOPERATION: MAJOR PROBLEMS FACING EAST ASIA AT PRESENT

World is now becoming united in which international community cannot live independently. The sovereignty of every States in the world cannot walk alone without having taken into consideration on the others States’ need and sovereignty. There are important issues of state sovereignty vs. international cooperation in regard of some grave problems facing our region, East Asia and even the world beyond. Among these issues are. the island disputes,  humanitarian intervention, TPP and trade and economic integration in general, including RCEP advocated by Indonesia, also global warming.All of these issues cannot be solved without international cooperation. Thus international cooperation is a must in the borderless era as we are experiencing today

A modified porous titanium sheet prepared by plasma activated sintering for biomedical applications

This study aimed to develop a contamination free porous titanium scaffold by a plasma activated sintering within an originally developed TiN coated graphite mold. The surface of porous titanium sheet with or without a coated graphite mold was characterized. The cell adhesion property of porous titanium sheet was also evaluated in this study. The peak of TiC was detected on the titanium sheet processed with the graphite mold without a TiN coating. Since the titanium fiber elements were directly in contact with the carbon graphite mold during processing, surface contamination was unavoidable event in this condition. The TiC peak was not detectable on the titanium sheet processed within the TiN coated carbon graphite mold. This modified plasma activated sintering with the TiN coated graphite mold would be useful to fabricate a contamination free titanium sheet. The number of adherent cells on the modified titanium sheet was greater than that of the bare titanium plate. Stress fiber formation and the extension of the cells were observed on the titanium sheets. This modified titanium sheet is expected to be a new tissue engineering material in orthopedic bone repair.Comment: 5 pages, 4 figure

Material-parameter Dependence of Superconductivity in High-temperature Cuprates

AbstractWe show that there is an interesting correlation between material parameters and critical temperature Tc in cuprate high temperature superconductors. Our analysis is based on the d-p model, that is, the three-band Hubbard model including d and p orbitals explicitly. This model contains many parameters; the transfer integrals tdp and tpp, the energy levels ɛp and ɛd, and the Coulomb interaction parameters Ud and Up. Our main results are the following: (a) Tc increases as ɛp−ɛd is increased for Up = 0, (2) Tc is lowered with increase of Up when ɛp−ɛd > 0, (3) Tc is increased with increase of Up when ɛp−ɛd < 0, (4) Tc has a minimum at near ɛp−ɛd = 0 as a function of ɛp−ɛd when Ud and Up are comparable, (5) Ud induces dx2-y2 pairing while Up induces dxy pairing, (6) Tc has a peak as a function of tpp. The results imply that Tc will increase if we can suppress Up. The role of Up is consistent with the experimental tendency that Tc increases as the relative ratio of the hole density at oxygen site to that at copper site is increased, which means that when Up increases, the number of p holes is decreased and Tc is also decreased