2,011 research outputs found
Momentum-Resolved Ultrafast Electron Dynamics in Superconducting Bi2Sr2CaCu2O8+delta
The non-equilibrium state of the high-Tc superconductor Bi2Sr2CaCu2O8+delta
and its ultrafast dynamics have been investigated by femtosecond time- and
angle-resolved photoemission spectroscopy well below the critical temperature.
We probe optically excited quasiparticles at different electron momenta along
the Fermi surface and detect metastable quasiparticles near the antinode. Their
decay through e-e scattering is blocked by a phase space restricted to the
nodal region. The lack of momentum dependence in the decay rates is in
agreement with relaxation dominated by Cooper pair recombination in a boson
bottleneck limit
Borealis sound an interactive wall for situational awareness: The impact of responsive architecture on users
This paper refers to the presence of visual communication elements in public spaces using interactive multimedia surfaces. The state of the art, the development of a proposal, and its evaluation are presented. The interactive surface applies to school of music “Escola de Música do Conservatório Nacional,” to which a design project was done in an academic context. The proposal aims to explore the incorporation of digital multimedia surfaces enhancing new dynamics while users walk in the interior of the building. Visual content will be displayed, and the interaction between users and the multimedia surfaces is done by the sounds produce by people and instruments. To assess the intuitive nature and relevance of the proposal, satisfaction and usability tests were conducted with the potential users. It was concluded that users appreciated the proposal and was able to perceive the effect people’s presence have in the interaction with the multimedia surface.info:eu-repo/semantics/acceptedVersio
Electron-phonon coupling in 122 Fe pnictides analyzed by femtosecond time-resolved photoemission
Based on results from femtosecond time-resolved photoemission, we compare
three different methods for determination of the electron-phonon coupling
constant {\lambda} in Eu and Ba-based 122 FeAs compounds. We find good
agreement between all three methods, which reveal a small {\lambda} < 0.2. This
makes simple electron-phonon mediated superconductivity unlikely in these
compounds.Comment: 11 pages, 3 figure
Momentum dependent ultrafast electron dynamics in antiferromagnetic EuFe2As2
Employing the momentum-sensitivity of time- and angle-resolved photoemission
spectroscopy we demonstrate the analysis of ultrafast single- and many-particle
dynamics in antiferromagnetic EuFe2As2. Their separation is based on a
temperature-dependent difference of photo-excited hole and electron relaxation
times probing the single particle band and the spin density wave gap,
respectively. Reformation of the magnetic order occurs at 800 fs, which is four
times slower compared to electron-phonon equilibration due to a smaller
spin-dependent relaxation phase space
Post-Outburst Observations of V1647 Ori: Detection of a Brief Warm, Molecular Outflow
We present new observations of the fundamental ro-vibrational CO spectrum of
V1647 Ori, the young star whose recent outburst illuminated McNeil's Nebula.
Previous spectra, acquired during outburst in 2004 February and July, had shown
the CO emission lines to be broad and centrally peaked-similar to the CO
spectrum of a typical classical T Tauri star. In this paper, we present CO
spectra acquired shortly after the luminosity of the source returned to its
pre-outburst level (2006 February) and roughly one year later (2006 December
and 2007 February). The spectrum taken in 2006 February revealed blue-shifted
CO absorption lines superimposed on the previously observed CO emission lines.
The projected velocity, column density, and temperature of this outflowing gas
was 30 km/s, 3^{+2}_{-1}E18 cm^{-2$, and 700^{+300}_{-100} K, respectively. The
absorption lines were not observed in the 2006 December and 2007 February data,
and so their strengths must have decreased in the interim by a factor of 9 or
more. We discuss three mechanisms that could give rise to this unusual outflow.Comment: 14 pages, 2 figures, accepted for publication in ApJ
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