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NEXT&極限&カデットプログラムジョイントセミナー

NEXT&極限&カデットプログラムジョイントセミナー

2013年11月19日

日時 2013年11月19日(火) 15:00-16:00
場所 基礎工学部D棟4階 D404-408 共用セミナー室
タイトル Conductive dense hydrogen
講師 Mikhail I. Eremets (Max Planck Institute for Chemistry, Mainz, Germany)

要旨
A strong motivation for study of solid hydrogen at high pressure is a predicted metallic state [1].This metal is expected to have remarkable properties such as high temperature superconductivity[2, 3].However hydrogen remained in the molecular state to the highest pressures of ~300 GPa and low temperature[4]. Recently conductive phase IV above 220 GPa and phase V above ~280 GPa were discovered at room temperature[5].Here we studied these phases in a wide temperature range. We performed Raman, infrared absorption, and electrical measurements at pressures up to 340 GPa.We have built a new phase diagram of hydrogen. In particular, we established a new triple point at the phase diagram at 208 GPa and T=308 K. Our new data as well as recent works[6, 7] further support the previous work[5] that hydrogen is semiconductor in phase IV and most likely semimetal in phase V.

References
[1] Wigner, E. and H.B. Huntington, On the possibility of a metallic modification of hydrogen. J. Chem. Phys., 1935. 3: p. 764-770.
[2] Ashcroft, N.W., Metallic hydrogen: A high-temperature superconductor Phys. Rev. Lett., 1968. 21: p. 1748-1750.
[3] McMahon, J.M. and D.M. Ceperley, High-temperature superconductivity in atomic metallic hydrogen. Phys Rev B, 2011. 84: p. 144515.
[4] Loubeyre, P., F. Occelli, and R. LeToullec, Optical studies of solid hydrogen to 320 GPa and evidence for black hydrogen. Nature, 2002. 416: p. 613-617.
[5] Eremets, M.I. and I.A. Troyan, Conductive dense hydrogen. Nature Materials, 2011. 10: p. 927-931.
[6] Cohen, R.E., I.I. Naumov, and R.J. Hemley, Electronic excitations and metallization of dense solid hydrogen. PNAS, 2013. 110
[7] Liu, H., et al., Room-temperature structures of solid hydrogen at high pressures. J. Chem. Phys. , 2012. 137.

連絡先:清水 克哉(極限量子科学研究センター・超高圧量子物性部門)
    内線6675・shimizu@cqst.osaka-u.ac.jp

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