Superconductivity in Hydrogen Dominant Materials: Silane

The metallization of hydrogen directly would require pressure in excess of 400 gigapascals (GPa), out of the reach of present experimental techniques. The dense group IVa hydrides attract considerable attention because hydrogen in these compounds is chemically precompressed and a metallic state is expected to be achievable at experimentally accessible pressures. We report the transformation of insulating molecular silane to a metal at 50 GPa, becoming superconducting at a transition temperature of Tc = 17 kelvin at 96 and 120 GPa. The metallic phase has a hexagonal close-packed structure with a high density of atomic hydrogen, creating a three-dimensional conducting network. These experimental findings support the idea of modeling metallic hydrogen with hydrogen-rich alloy.

[1]  N. Ashcroft,et al.  METALLIC HYDROGEN: A HIGH-TEMPERATURE SUPERCONDUCTOR. , 1968 .

[2]  R. Martin,et al.  Metallization of molecular hydrogen: predictions from exact-exchange calculations. , 2000, Physical review letters.

[3]  Paul Loubeyre,et al.  Optical studies of solid hydrogen to 320 GPa and evidence for black hydrogen , 2002, Nature.

[4]  E. Wigner,et al.  On the Possibility of a Metallic Modification of Hydrogen , 1935 .

[5]  N. Ashcroft.  Hydrogen dominant metallic alloys: high temperature superconductors? , 2004, Physical review letters.

[6]  W. Nellis,et al.  Dynamic compression of materials: metallization of fluid hydrogen at high pressures , 2006 .

[7]  Neil W. Ashcroft,et al.  Structure and bandgap closure in dense hydrogen , 2000, Nature.

[8]  Yang Song,et al.  Crystal structure ofSiH4at high pressure , 2007 .

[9]  Chris J Pickard,et al.  High-pressure phases of silane. , 2006, Physical review letters.

[10]  Wojciech Grochala,et al.  Pressure induced metallization of Germane , 2006 .

[11]  A. Bergara,et al.  No evidence of metallic methane at high pressure , 2006 .

[12]  G. Stupian,et al.  Optical properties of methane to 288 GPa at 300 K , 2006 .

[13]  A. Cabana,et al.  Vibrational Spectra of SiH4 and SiD4–SiH4 Mixtures in the Condensed States , 1972 .

[14]  J. Ashby.  References and Notes , 1999 .

[15]  Ruoff,et al.  Experimental study of the crystal stability and equation of state of Si to 248 GPa. , 1990, Physical review. B, Condensed matter.

[16]  H. Mao,et al.  X-ray diffraction and equation of state of hydrogen at megabar pressures , 1996, Nature.

[17]  Roald Hoffmann,et al.  Structures and Potential Superconductivity in SiH~4 at High Pressure: En Route to "Metallic Hydrogen" , 2006 .

[18]  Yanming Ma,et al.  Superconductivity in high-pressure SiH4 , 2007 .

[19]  Stefano de Gironcoli,et al.  Phonons and related crystal properties from density-functional perturbation theory , 2000, cond-mat/0012092.

[20]  Russell J. Hemley,et al.  Ultrahigh-pressure transitions in solid hydrogen , 1994 .

[21]  K Tanaka,et al.  Novel superconductivity in metallic SnH(4) under high pressure. , 2007, Physical review letters.