1,147 research outputs found
Peak effect and dynamic melting of vortex matter in NbSe crystals
We present a mode locking (ML) phenomenon of vortex matter observed around
the peak effect regime of 2H-NbSe pure single crystals. The ML features
allow us not only to trace how the shear rigidity of driven vortices persists
on approaching the second critical field, but also to demonstrate a dynamic
melting transition of driven vortices at a given velocity. We observe the
velocity dependent melting signatures in the peak effect regime, which reveal a
crossover between the disorder-induced transition at small velocity and the
thermally induced transition at large velocity. This uncovers the relationship
between the peak effect and the thermal melting.Comment: To appear in Physical Review Lette
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Lost Apollo heat flow data suggest a different lunar bulk composition
Lunar surface heat flow values were measured on the Apollo missions between 1971 and 1977. However, the late-term data have been lost. We succeeded in archiving the data after March 1, 1976. We will introduce the new set of archived data
Dynamic ordering of driven vortex matter in the peak effect regime of amorphous MoGe films and 2H-NbSe2 crystals
Dynamic ordering of driven vortex matter has been investigated in the peak
effect regime of both amorphous MoGe films and 2H-NbSe2 crystals by mode
locking (ML) and dc transport measurements. ML features allow us to trace how
the shear rigidity of driven vortices evolves with the average velocity.
Determining the onset of ML resonance in different magnetic fields and/or
temperatures, we find that the dynamic ordering frequency (velocity) exhibits a
striking divergence in the higher part of the peak effect regime.
Interestingly, this phenomenon is accompanied by a pronounced peak of dynamic
critical current. Mapping out field-temperature phase diagrams, we find that
divergent points follow well the thermodynamic melting curve of the ideal
vortex lattice over wide field and/or temperature ranges. These findings
provide a link between the dynamic and static melting phenomena which can be
distinguished from the disorder induced peak effect.Comment: 9 pages, 6 figure
Observation of an energetic radiation burst from mountain-top thunderclouds
During thunderstorms on 2008 September 20, a simultaneous detection of gamma
rays and electrons was made at a mountain observatory in Japan located 2770 m
above sea level. Both emissions, lasting 90 seconds, were associated with
thunderclouds rather than lightning. The photon spectrum, extending to 10 MeV,
can be interpreted as consisting of bremsstrahlung gamma rays arriving from a
source which is 60 - 130 m in distance at 90% confidence level. The observed
electrons are likely to be dominated by a primary population escaping from an
acceleration region in the clouds.Comment: 12 pages, 3 figures, accepted for publication in Physical Review
Letter
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