10,562 research outputs found
Studies of superconductivity and structure for CaC6 to pressures above 15 GPa
The dependence of the superconducting transition temperature Tc of CaC6 has
been determined as a function of hydrostatic pressure in both helium-loaded gas
and diamond-anvil cells to 0.6 and 32 GPa, respectively. Following an initial
increase at the rate +0.39(1) K/GPa, Tc drops abruptly from 15 K to 4 K at 10
GPa. Synchrotron x-ray measurements to 15 GPa point to a structural transition
near 10 GPa from a rhombohedral to a higher symmetry phase
Superconductivity at 17 K in Yttrium Metal under Nearly Hydrostatic Pressures to 89 GPa
In an experiment in a diamond anvil cell utilizing helium pressure medium,
yttrium metal displays a superconducting transition temperature which increases
monotonically from Tc ? 3.5 K at 30 GPa to 17 K at 89.3 GPa, one of the highest
transition temperatures for any elemental superconductor. The pressure
dependence of Tc differs substantially from that observed in previous studies
under quasihydrostatic pressure to 30 GPa. Remarkably, the dependence of Tc on
relative volume V/Vo is linear over the entire pressure range above 33 GPa,
implying that higher values of Tc are likely at higher pressures. For the
trivalent metals Sc, Y, La, Lu there appears to be some correlation between Tc
and the ratio of the Wigner-Seitz radius to the ion core radius.Comment: submitted for publicatio
The Static Quark-Antiquark Potential: A ``Classical'' Experiment On The Connection Machine CM-2
We describe the Wuppertal university pilot project in applied parallel
computing. We report on a comprehensive high statistics determination of the
static quark-antiquark potential and related quantities from quenched quantum
chromodynamics. New data for the string tension and the plaquette action for
the region 5.5 < beta < 6.8 is presented.Comment: (Talk K. Schilling), 11 pages, postscript (\approx 250K
Inhomogeneous lattice paths, generalized Kostka polynomials and A supernomials
Inhomogeneous lattice paths are introduced as ordered sequences of
rectangular Young tableaux thereby generalizing recent work on the Kostka
polynomials by Nakayashiki and Yamada and by Lascoux, Leclerc and Thibon.
Motivated by these works and by Kashiwara's theory of crystal bases we define a
statistic on paths yielding two novel classes of polynomials. One of these
provides a generalization of the Kostka polynomials while the other, which we
name the A supernomial, is a -deformation of the expansion
coefficients of products of Schur polynomials. Many well-known results for
Kostka polynomials are extended leading to representations of our polynomials
in terms of a charge statistic on Littlewood-Richardson tableaux and in terms
of fermionic configuration sums. Several identities for the generalized Kostka
polynomials and the A supernomials are proven or conjectured. Finally,
a connection between the supernomials and Bailey's lemma is made.Comment: 44 pages, figures, AMS-latex; improved version to appear in Commun.
Math. Phys., references added, some statements clarified, relation to other
work specifie
Pressure-Induced Superconductivity in Sc to 74 GPa
Using a diamond anvil cell with nearly hydrostatic helium pressure medium we
have significantly extended the superconducting phase diagram Tc(P) of Sc, the
lightest of all transition metals. We find that superconductivity is induced in
Sc under pressure, Tc increasing monotonically to 8.2 K at 74.2 GPa. The Tc(P)
dependences of the trivalent d-electron metals Sc, Y, La, and Lu are compared
and discussed within a simple s-d charge transfer framework.Comment: to be published in Phys. Rev. B (Brief Reports
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