203 research outputs found
Microwave Induced Instability Observed in BSCCO 2212 in a Static Magnetic Field
We have measured the microwave dissipation at 10 GHz through the imaginary
part of the susceptibility, , in a BSCCO 2212 single crystal in an
external static magnetic field parallel to the c-axis at various fixed
temperatures. The characteristics of exhibit a sharp step at a
field which strongly depends on the amplitude of the microwave
excitation . The characteristics of vs. ,
qualitatively reveal the behavior expected for the magnetic field dependence of
Josephson coupling.Comment: 4 pages, 3 Postscript figure
Two-gap superconductivity in single crystal LuFeSi from penetration depth measurements
Single crystal of LuFeSi was studied with the tunnel-diode
resonator technique in Meissner and mixed states. Temperature dependence of the
superfluid density provides strong evidence for the two-gap superconductivity
with almost equal contributions from each gap of magnitudes
and . In the vortex state, pinning
strength shows unusually strong temperature dependence and is non-monotonic
with the magnetic field (peak effect). The irreversibility line is sharply
defined and is quite distant from the , which hints on to enhanced
vortex fluctuations in this two-gap system. Altogether our findings provide
strong electromagnetic - measurements support to the two-gap superconductivity
in LuFeSi previously suggested from specific heat measurements
Specific heat evidence for two-gap superconductivity in ternary-iron silicide LuFeSi
We report low-temperature specific heat studies on single-crystalline
ternary-iron silicide superconductor LuFeSi with = 6.1 K
down to . We confirm a reduced normalized jump in specific heat at
, and find that the specific heat divided by temperature shows
sudden drop at and goes to zero with further decreasing
temperature. These results indicate the presence of two distinct
superconducting gaps in LuFeSi, similar to a typical two-gap
superconductor MgB. We also report Hall coefficients, band structure
calculation, and the anisotropy of upper critical fields for
LuFeSi, which support the anisotropic multiband nature and
reinforce the existence of two superconducting gaps in
LuFeSi.Comment: 5 pages, 5 figure
Multivalued memory effects in electronic phase-change manganites controlled by Joule heating
Non-volatile multivalued memory effects caused by magnetic fields, currents,
and voltage pulses are studied in Nd_{0.65}Ca_{0.35}MnO_3 and
(Nd_{1-y}Sm_{y})_{0.5}Sr_{0.5}MnO_3 (y=0.75) single crystals in the hysteretic
region between ferromagnetic metallic and charge-ordered insulating states. The
current/voltage effects observed in this study are explained by the
self-heating effect, which enable us to control the colossal electroresistance
effects. This thermal-cycle induced switching between electronic solid and
liquid states can be regarded as electronic version of atomic crystal/amorphous
transitions in phase-change chalcogenides.Comment: 5 pages, 4 figures. to appear in Phys. Rev.
Two-band superconductivity featuring different anisotropies in the ternary iron silicide LuFeSi
We report detailed studies of the upper critical field and low-temperature
specific heat in the two-gap superconductor LuFeSi. The
anisotropy of the upper critical field suggests that the active band is
quasi-one-dimensional. Low-temperature specific heat in magnetic fields reveals
that the virtual in the passive band is almost isotropic. These
results strongly indicate that the two bands have two different anisotropies,
similar to the typical two-gap superconductor MgB, and their interplay
may be essential to the two-gap superconductivity in LuFeSi.Comment: 5 pages, 5 figure
Equilibrium First-Order Melting and Second-Order Glass Transitions of the Vortex Matter in BiSrCaCuO
The thermodynamic phase diagram of BiSrCaCuO was mapped
by measuring local \emph{equilibrium} magnetization in presence of
vortex `shaking'. Two equally sharp first-order magnetization steps are
revealed in a single temperature sweep, manifesting a liquid-solid-liquid
sequence. In addition, a second-order glass transition line is revealed by a
sharp break in the equilibrium slope. The first- and second-order lines
intersect at intermediate temperatures, suggesting the existence of four
phases: Bragg glass and vortex crystal at low fields, glass and liquid at
higher fields.Comment: 5 pages, 4 figures. To be published in Phys. Rev. Let
Interplay of Anisotropy and Disorder in the Doping-Dependent Melting and Glass Transitions of Vortices in BiSrCaCuO
We study the oxygen doping dependence of the equilibrium first-order melting
and second-order glass transitions of vortices in
BiSrCaCuO. Doping affects both anisotropy and
disorder. Anisotropy scaling is shown to collapse the melting lines only where
thermal fluctuations are dominant. Yet, in the region where disorder breaks
that scaling, the glass lines are still collapsed. A quantitative fit to
melting and replica symmetry breaking lines of a 2D Ginzburg-Landau model
further reveals that disorder amplitude weakens with doping, but to a lesser
degree than thermal fluctuations, enhancing the relative role of disorder.Comment: 4 pages, 4 figure
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