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under high pressureTateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yamamoto, Etsuji; Okuda, Yusuke*; Miyauchi, Yuichiro*; Settai, Rikio*; Onuki, Yoshichika
Journal of Physics; Conference Series, 121(5), p.052001_1 - 052001_5, 2008/07
Times Cited Count：2 Percentile：60.82(Physics, Multidisciplinary)We investigated the pressure-induced superconductor CeIrSi without inversion center under high pressure. The electrical resistivity and ac heat capacity were measured in the same run for the same sample. The critical pressure of the antiferromagnetic state was determined to be 
= 2.25 GPa. The co-existence of the antiferromagnetism and superconductivity is discussed. The superconducting region is extended up to about 3.5 GPa. The superconducting transition temperature 
shows a maximum value of 1.6 K around 
GPa. At 2.58 GPa, a large heat capacity anomaly was observed at = 1.59 K. The jump of the heat capacity in the form of 
is 5.7 
0.1. This is the largest observed value among all superconductors studied previously, suggesting the strong-coupling superconductivity in CeIrSi.
Katayama, Yoshinori; Hattori, Takanori; Saito, Hiroyuki; Aoki, Katsutoshi; Fukui, Hiroshi*; Funakoshi, Kenichi*
no journal, ,
The unique properties of liquid water are related hydrogen bonded network structure. Simulation studies predicted drastic changes such as weakening of hydrogen-bonded network structure and molecular dissociation in a pressure range from a few GPa to a few tens GPa. We have measured in-situ X-ray diffraction of liquid water just above the melting temperature at pressures up to 17 GPa using a cubic-type multi-anvil press on BL14B1 beamline and a Kawai-type double-stage press on BL04B1 beamline at SPring-8 synchrotron radiation facility. Below 5 GPa, the coordination number of water molecules rapidly increased to about 9 while inter-molecular distance stayed almost constant. In other words, the local structure changed to a simple structure with increasing pressure. Above this pressure, the volume reduction was attributed to a decreased of inter-molecular distance.
Aoki, Katsutoshi; Machida, Akihiko; Omura, Ayako*; Watanuki, Tetsu; Takemura, Kenichi*
no journal, ,
Structural investigation on metal hydrides provides an insight into the interactions between hydrogen atoms occupying the interstitial spaces of a metal lattice. The hydrogen atoms are often negatively ionized due to the charge transfer from the host metal lattice and the electrostatic forces play a dominant role in structural stabilization or transition. Synchrotron X-ray diffraction measurements were made for di-hydrides and tri-hydrides of rare-earth metals (Sc, Y, La) at pressures up to 50 GPa and at ambient pressure at SPring-8.
