Superconductivity in the Silicon Clathrate Compound (Na,Ba)xSi46

Abstract

A new silicon clathrate compound containing barium, (Na, Ba),Si46, becomes a type-II superconductor with a critical temperature (T,) of about 4 K. In the compound, the silicon atoms are bonded tetrahedrally with about the same bond distances as in ordinary cubic diamond Si, but form 12and 14-hedral cages which are linked by shared faces. The metal atoms are located in the center of the polyhedra. This is the erst superconductor consisting of a Si sp' covalent network.PACS numbers: 74. 10.+v, 61.66.Fn, 74.70.Ad Silicon and carbon are often discussed in comparison with each other in terms of the same group-IV elements.As for elemental carbon, there are two allotropes, diamond and graphite, and recently fullerene has been added as a new member [1]; only the diamond type structure is known for elemental silicon. The recent discovery

Structural and electronic properties of germanium clathratesGe46andK8Zhao1, Buldum2, Lu3 et al. 1999Phys. Rev. B21391View full textAdd to dashboardCite

“…This difference also corresponds to the DOS and other electronic properties. A high DOS peak at Fermi energy is found for Na 2 Ba 6 Ge 46 9 and this material is superconducting 6 . In comparison, the DOS at Fermi level for K 8 Ge 46 is moderate and it is not superconducting.…”

Pressure-induced phase transformations in theBa8Si46clathrate

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Very low compressibility in a Na-doped Si clathrate with the type-II structure was first reported, 12 which transforms into an amorphous phase at ϳ12 GPa. In contrast, the type-I Si 46 clathrates of K ͑Ref.…”

Effect of electron-phonon coupling on the superconducting transition temperature in dodecaboride superconductors: A comparison ofLuB12withZrB12Teyssier1, Lortz2, Petrović3 et al. 2008Phys. Rev. B464410View full textAdd to dashboardCite

“…7,8 Apart from the borides, superconductors with similar structures are found, for example, among the pyrochlores 9,10 or the clathrates. [11][12][13][14] Strong covalent bonds between the boron atoms in B 12 cages lead to a very rigid lattice with a high Debye temperature. The size of the caged atom only has a minor effect on the lattice parameter; however the presence of the metal atoms stabilizes the structure since two valence electrons per metal atom are transferred to the cages in order to compensate the electron deficiency in the boron sublattice.…”