649 research outputs found
Multilayer Thermionic Refrigerator and Generator
A new method of refrigeration is proposed. Cooling is obtained by thermionic
emission of electrons over periodic barriers in a multilayer geometry. These
could be either Schottky barriers between metals and semiconductors or else
barriers in a semiconductor superlattice. The same device is an efficient power
generator. A complete theory is provided.Comment: 17 pages with 5 postscript figures, submitted to J. Appl. Phy
Sudden vanishing and reappearance of nonclassical effects: General occurrence of finite-time decays and periodic vanishings of nonclassicality and entanglement witnesses
Analyses of phenomena exhibiting finite-time decay of quantum entanglement
have recently attracted considerable attention. Such decay is often referred to
as sudden vanishing (or sudden death) of entanglement, which can be followed by
its sudden reappearance (or sudden rebirth). We analyze various finite-time
decays (for dissipative systems) and analogous periodic vanishings (for unitary
systems) of nonclassical correlations as described by violations of classical
inequalities and the corresponding nonclassicality witnesses (or quantumness
witnesses), which are not necessarily entanglement witnesses. We show that
these sudden vanishings are universal phenomena and can be observed: (i) not
only for two- or multi-mode but also for single-mode nonclassical fields, (ii)
not solely for dissipative systems, and (iii) at evolution times which are
usually different from those of sudden vanishings and reappearances of quantum
entanglement.Comment: 10 pages, 3 figure
Magnetic Breakdown in the electron-doped cuprate superconductor NdCeCuO: the reconstructed Fermi surface survives in the strongly overdoped regime
We report on semiclassical angle-dependent magnetoresistance oscillations
(AMRO) and the Shubnikov-de Haas effect in the electron-overdoped cuprate
superconductor NdCeCuO. Our data provide convincing evidence
for magnetic breakdown in the system. This shows that a reconstructed
multiply-connected Fermi surface persists, at least at strong magnetic fields,
up to the highest doping level of the superconducting regime. Our results
suggest an intimate relation between translational symmetry breaking and the
superconducting pairing in the electron-doped cuprate superconductors.Comment: 5 pages, 4 figures, submitted to PR
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