629 research outputs found
Vortex Softening: Origin of the second peak effect in BiSrCaCuO
Transverse ac permeability measurements in BiSrCaCuO single crystals at low fields and temperatures in a vortex configuration
free of external forces show that the decrease of the critical current as
measured by magnetization loops at the second peak effect is an artifact due to
creep. On the other hand, the increase of critical current at the second peak
is due to a genuine softening of the tilting elastic properties of vortices in
the individual pinning regime that precedes the transition to a disorder state.Comment: 4 pages, 5 figures, RevTex, two column versio
Berry phase jumps and giant nonreciprocity in Dirac quantum dots
We predict that a strong nonreciprocity in the resonance spectra of Dirac
quantum dots can be induced by the Berry phase. The nonreciprocity arises in
relatively weak magnetic fields and is manifest in anomalously large
field-induced splittings of quantum dot resonances which are degenerate at
due to time-reversal symmetry. This exotic behavior, which is governed by
field-induced jumps in the Berry phase of confined electronic states, is unique
to quantum dots in Dirac materials and is absent in conventional quantum dots.
The effect is strong for gapless Dirac particles and can overwhelm the
-induced orbital and Zeeman splittings. A finite Dirac mass suppresses the
effect. The nonreciprocity, predicted for generic two-dimensional Dirac
materials, is accessible through Faraday and Kerr optical rotation measurements
and scanning tunneling spectroscopy.Comment: 6 pages, 6 figure
The chemical composition of the Orion star forming region: stars, gas and dust
We present a summary of main results from the studies performed in the series
of papers "The chemical composition of the Orion star forming region". We
reinvestigate the chemical composition of B-type stars in the Orion OB1
association by means of state-of-the-art stellar atmosphere codes, atomic
models and techniques, and compare the resulting abundances with those obtained
from the emission line spectra of the Orion nebula (M42), and recent
determinations of the Solar chemical composition.Comment: 5 pages, 4 figures, 2 tables. Poster contribution to the proceedings
of the LIAC2010 conference "The multi-wavelength view of hot, massive stars
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