506 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
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
Fermi-surface topology of the iron pnictide LaFeP
We report on a comprehensive de Haas--van Alphen (dHvA) study of the iron
pnictide LaFeP. Our extensive density-functional band-structure
calculations can well explain the measured angular-dependent dHvA frequencies.
As salient feature, we observe only one quasi-two-dimensional Fermi-surface
sheet, i.e., a hole-like Fermi-surface cylinder around , essential for
pairing, is missing. In spite of considerable mass enhancements due to
many-body effects, LaFeP shows no superconductivity. This is likely
caused by the absence of any nesting between electron and hole bands.Comment: 5 pages, 4 figure
Dimensionality dependent electronic structure of the exfoliated van der Waals antiferromagnet NiPS
Resonant Inelastic X-ray Scattering (RIXS) was used to measure the local
electronic structure in few-layer exfoliated flakes of the van der Waals
antiferromagnet NiPS. The resulting spectra show a systematic softening and
broadening of multiplet excitations with decreasing layer count from
the bulk to three atomic layers (3L). These trends are driven by a decrease in
the transition metal-ligand and ligand-ligand hopping integrals, and in the
charge-transfer energy: = 0.60 eV in the bulk and 0.22 eV in 3L
NiPS. Relevant intralayer magnetic exchange integrals computed from the
electronic parameters exhibit a systematic decrease in the average interaction
strength with thickness and place 2D NiPS close to the phase boundary
between stripy and spiral antiferromagnetic order, which may explain the
apparent vanishing of long-range order in the 2D limit. This study explicitly
demonstrates the influence of layer electronic interactions on
layer ones in insulating magnets. As a consequence, the magnetic
Hamiltonian in few-layer insulating magnets can be significantly different from
that in the bulk.Comment: 5 pages, 4 figures; additional 9 pages and 13 figures of
supplementary informatio
Ground state of the S = triangular lattice Heisenberg-like antiferromagnet Ba CoSb O in an out-of-plane magnetic field
HFM EXED The High Magnetic Field Facility for Neutron Scattering at BER II
An overview of the high magnetic field facility for neutron scattering at Helmholtz Zentrum Berlin HZB is given. The facility enables elastic and inelastic neutron scattering experiments in continuous magnetic fields up to 26.3 T combined with temperatures down to 0.6
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