Superconductivity in Boron and related materials at megabar pressures.
M. I. Eremets
Max Planck Inst. fur Chemie, Postfach 3060, 55020 Mainz,Germany
We performed electrical and optical measurements at pressures up to 260 GPa and down to millikelvin temperatures to study metallization and searching for superconductivity in a number of elemental and simple substances: S, Se, Xe, CsI and others. In the report, we will focus on superconductivity in boron and also on electrical properties of nitrogen and hydrogen at megabar pressures.
Superconductivity in the Pyrochlore Oxide Cd2Re2O7
Hiroi Zenji
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
Pyrochlore oxides belong to one of the largest structural groups for transition metal oxides. Although many metallic pyrochlore oxides have been known, there were no compounds to exhibit superconductivity so far. Recently superconductivity at Tc = 1.0 K was found in Cd2Re2O7. The following experimental results have revealed a unique correlation between the crystal and electronic structures for the itinerant electron system in the pyrochlore lattice.
Superconductivity in Pyrochlore-Type Frustrated Spin System, Cd2Re2O7
Kazuyoshi Yoshimura
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
Recently, the geometrical frustration in strongly correlated electron system has been attracted considerable interest. The pyrochlore oxides which have a general formula, A2B2O6O' contain tetrahedral networks of A and B cations, leading to a geometrical frustration. Some of them exhibit a wide variety of physical properties from insulating through semiconducting and bad metallic toward good metallic. Among them, Cd2Re2O7 has newly been reported to exhibit the type II superconductivity at 1.1 K [1, 2]. Here, we report our discovery [1] of the occurrence of superconductivity in the pyrochlore-type frustrated spin system, Cd2Re2O7. Furthermore, its physical properties will be reviewed.
[1] H. Sakai, K. Yoshimura et al., J. Phys.: Condens. Matter 13(2001) L785-L790.
[2] M. Hanawa, Z. Hiroi et al., Phys.Rev. Lett. 87 (2001) 187001.
Superconductivity in Ropes of Single-Walled Carbon Nanotubes
A.Yu. Kasumova, M. Kociakb, M. Ferrierb, Yu.A. Kasumovc, S. Gueronb, B. Reuletb, I.I. Khodosc, Yu.B. Gorbatovc, V.T. Volkovc, L. Vaccarinid, H. Bouchiatb
aPresent address: RIKEN, Hirosawa 2-1, Wako, Saitama 351-0198, Japan
bLaboratoire de Physique des Solides, Associe au CNRS, 510, Universite Paris-Sud, 91405, Orsay, France
cInstitute of Microelectronics Technology, RAS, Chernogolovka 142432 Moscow Reg., Russia
dGroupe de Dynamique des Phases Condensees, Universite Montpellier, II 34095 Montpellier, France
We report measurements on ropes of single-walled carbon nanotubes (SWNT) in low-resistance contact to nonsuperconducting metallic pads, at low voltage and at temperatures down to 13 mK. Large resistance drops and strong non-linearities in the IV characteristics are observed below 0.4K. These features, which disappear in magnetic field in the Tesla range, strongly suggest the existence of superconductivity in ropes of SWNT.
NMR studies of the electron-doped hafnium nitride superconductor
Hideki Toua, Yutaka Maniwab, Shoji Yamanakac
aDepartment of Quantum matters, AdSM, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, 739-8526, Japan
bDepartment of Physics, Tokyo Metropolitan University, Minami-osawa, Hachi-oji, Tokyo, 192-0397, Japan
cDepartment of Applied Chemistry, Graduate school of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
NMR measurements were carried out on recently discovered layered superconductor Li0.48(THF)yHfNCl. 7Li-NMR results suggests that the Fermi level density of states at intermidiated Li site are considerably small and the superconductivity is derived from the HfNCl layer.