June 24, 1998


    A group led by Professor Kiichi Amaya of Osaka University (guest researcher in the Research Group for Quantum Condensed Matter Systems, Advanced Science Research Center, the Japan Atomic Energy Research Institute) discovered that superconductivity exists in solid oxygen at extremely low temperatures and under conditions of ultra-high pressure.
This result comes from research conducted by scientists at the Advanced Science Research Center of the Japan Atomic Energy Research Institute (JAERI), and the Core Research for Evolutional Science and Technology (CREST) Project of the Japan Science and Technology Corporation (JST).

    Oxygen was cooled under a pressure of 1 - 1.25 million atmospheres and a rapid decrease in electric resistance was observed at 0.6K.Tests were conducted to detect the change in strength in the magnetic field and in the Meissner effect at the phase transition, and it was concluded that metallic oxygen exhibits superconductivity at temperatures lower than 0.6K.It was also made clear that the critical magnetic field where superconductivity disappears is 0.15 tesla and the pressure change at the transition to superconductivity is negligible under pressures of between 1 and 1.25 million atmospheres. The transition temperature Tc of elements in this group on the periodic table rises with decrease of atomic numbers in the order of tellurium, selenium, and sulfur - with the Tc of sulfur the highest in the elementary metals in this group.However, oxygen, an element located on the row of the smallest atomic number, shows a very low Tc value of 0.6K. The reason for this irregularity is not clear. The impact of this finding was so strong that it was reported in "Nature,"in the June 25, 1998 issue.

For further information, contact:Dr. Naoto Metoki
Advanced Science Research Center
Tel: +81-29-282-6729
Fax: +81-29-282-6716
E-mail: metoki@kotai3.tokai.jaeri.go.jp

Dr. Akio Ishida,
Dept. of CREST, JST
Tel: +81-48-226-5635
Fax: +81-48-226-1164
E-mail: ishida@jst.go.jp

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