4,167 research outputs found
Topology effects on the heat capacity of mesoscopic superconducting disks
Phase transitions in superconducting mesoscopic disks have been studied over
the H-T phase diagram through heat capacity measurement of an array of
independent aluminium disks. These disks exhibit non periodic modulations
versus H of the height of the heat capacity jump at the superconducting to
normal transition. This behaviour is attributed to giant vortex states
characterized by their vorticity L. A crossover from a bulk-like to a
mesoscopic behaviour is demonstrated. versus H plots exhibit
cascades of phase transitions as L increases or decreases by one unity, with a
strong hysteresis. Phase diagrams of giant vortex states inside the
superconducting region are drawn in the vortex penetration and expulsion
regimes and phase transitions driven by temperature between vortex states are
thus predicted in the zero field cooled regime before being experimentally
evidenced
UNLV Wind Orchestra & Green Valley High Symphonic Band
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Surface-induced near-field scaling in the Knudsen layer of a rarefied gas
We report on experiments performed within the Knudsen boundary layer of a
low-pressure gas. The non-invasive probe we use is a suspended
nano-electro-mechanical string (NEMS), which interacts with He gas at
cryogenic temperatures. When the pressure is decreased, a reduction of the
damping force below molecular friction had been first reported in
Phys. Rev. Lett. Vol 113, 136101 (2014) and never reproduced since. We
demonstrate that this effect is independent of geometry, but dependent on
temperature. Within the framework of kinetic theory, this reduction is
interpreted as a rarefaction phenomenon, carried through the boundary layer by
a deviation from the usual Maxwell-Boltzmann equilibrium distribution induced
by surface scattering. Adsorbed atoms are shown to play a key role in the
process, which explains why room temperature data fail to reproduce it.Comment: Article plus supplementary materia
Thermal signatures of Little-Parks effect in the heat capacity of mesoscopic superconducting rings
We present the first measurements of thermal signatures of the Little-Parks
effect using a highly sensitive nanocalorimeter. Small variations of the heat
capacity of 2.5 millions of non interacting micrometer-sized
superconducting rings threaded by a magnetic flux have been measured by
attojoule calorimetry. This non-invasive method allows the measurement of
thermodynamic properties -- and hence the probing of the energy levels -- of
nanosystems without perturbing them electrically. It is observed that is
strongly influenced by the fluxoid quantization (Little-Parks effect) near the
critical temperature . The jump of at the superconducting phase
transition is an oscillating function of with a period ,
the magnetic flux quantum, which is in agreement with the Ginzburg-Landau
theory of superconductivity.Comment: To be published in Physical Review B, Rapid Communication
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Caring for someone dying at home
Assisting those caring for a terminally ill family member at home can be a rewarding but challenging nursing experience. Providing adequate nursing support is critical to the success of this type of caring
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