1,537 research outputs found
The emergence of superconductivity in BaNi2(Ge1-xPx)2 at a structural instability
The physical properties and structural evolution of the 122-type solid
solution BaNi2(Ge1-xPx)2 are reported. The in-plane X-X (X = Ge1-xPx) dimer
formation present in the end member BaNi2Ge2, which results in a structural
transition to orthorhombic symmetry, is completely suppressed to zero
temperature on P substitution near x = 0.7, and a dome-shape superconducting
phase with a maximum Tc = 2.9 K emerges. Clear indications of phonon softening
and enhanced electron-phonon coupling are observed at the composition of the
structural instability. Our findings show that dimer breaking offers new
possibilities as a tuning parameter of superconductivity.Comment: 14 pages, 4 figure
On the energy saved by interlayer interactions in the superconducting state of cuprates
A Ginzburg-Landau-like functional is proposed reproducing the main low-energy
features of various possible high-Tc superconducting mechanisms involving
energy savings due to interlayer interactions. The functional may be used to
relate these savings to experimental quantities. Two examples are given,
involving the mean-field specific heat jump at Tc and the superconducting
fluctuations above Tc. Comparison with existing data suggests, e.g., that the
increase of Tc due to the so-called interlayer tunneling (ILT) mechanism of
interlayer kinetic-energy savings is negligible in optimally-doped Bi-2212.Comment: 12 pages, no figures. Version history: 21-aug-2003, first version
(available on http://arxiv.org/abs/cond-mat/0308423v1); 15-jan-2004, update
to match Europhys. Lett. publication (minor grammar changes, updates in
bibliography - e.g., refs. 5 and 26
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