112 research outputs found
Magnetism and superconductivity in strongly correlated CeRhIn5
Specific heat studies of CeRhIn5 as functions of pressure and magnetic field
have been used to explore the relationship between magnetism and unconventional
superconductivity, both of which involve the 4f electron of Ce. Results of
these studies cannot be understood as a simple competition for Fermi-surface
states and require a new conceptual framework.Comment: 9 pages, 7 figure
Pressure effects on the superconducting thin film BaKFeAs
We report electrical resistivity measurements on a high-quality
BaKFeAs thin film () under pressure. The
superconducting transition temperature (=39.95 K) of the optimally-doped thin
film shows a dome shape with pressure, reaching a maximal value 40.8 K at 11.8
kbar. The unusually high superconducting transition temperature and its
anomalous pressure dependence are ascribed to a lattice mismatch between the
LaAlO substrate and the thin film. The local temperature exponent of the
resistivity () shows a funnel shape around
the optimal pressure, suggesting that fluctuations associated with the
anomalous normal state are responsible for high-temperature superconductivity.Comment: To appear in Appl. Phys. Let
Presure-Induced Superconducting State of Antiferromagnetic CaFeAs
The antiferromagnet CaFeAs does not become superconducting when
subject to ideal hydrostatic pressure conditions, where crystallographic and
magnetic states also are well defined. By measuring electrical resistivity and
magnetic susceptibility under quasi-hydrostatic pressure, however, we find that
a substantial volume fraction of the sample is superconducting in a narrow
pressure range where collapsed tetragonal and orthorhombic structures coexist.
At higher pressures, the collapsed tetragonal structure is stabilized, with the
boundary between this structure and the phase of coexisting structures strongly
dependent on pressure history. Fluctuations in magnetic degrees of freedom in
the phase of coexisting structures appear to be important for
superconductivity.Comment: revised (6 pages, 5 figures) - includes additional experimental
result
Anomalous Pressure Dependence of Kadowaki-Woods ratio and Crystal Field Effects in Mixed-valence YbInCu4
The mixed-valence (MV) compound YbInCu4 was investigated by electrical
resistivity and ac specific heat at low temperatures and high pressures. At
atmospheric pressure, its Kadowaki-Woods (KW) ratio, A/\gamma ^2, is 16 times
smaller than the universal value R_{KW}(=1.0 x 10^-5 \mu \Omega cm mol^2 K^2
mJ^-2), but sharply increases to 16.5R_{KW} at 27 kbar. The pressure-induced
change in the KW ratio and deviation from R_{KW} are analyzed in terms of the
change in f-orbital degeneracy N and carrier density n. This analysis is
further supported by a dramatic change in residual resistivity \rho_0 near 25
kbar, where \rho_0 jumps by a factor of 7.Comment: 4pages, 3figure
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