41,414 research outputs found
Room temperature ferromagnetic-like behavior in Mn-implanted and post-annealed InAs layers deposited by Molecular Beam Epitaxy
We report on the magnetic and structural properties of Ar and Mn implanted
InAs epitaxial films grown on GaAs (100) by Molecular Beam Epitaxy (MBE) and
the effect of Rapid Thermal Annealing (RTA) for 30 seconds at 750C. Channeling
Particle Induced X- ray Emission (PIXE) experiments reveal that after Mn
implantation almost all Mn atoms are subsbtitutional in the In-site of the InAs
lattice, like in a diluted magnetic semiconductor (DMS). All of these samples
show diamagnetic behavior. But, after RTA treatment the Mn-InAs films exhibit
room-temperature magnetism. According to PIXE measurements the Mn atoms are no
longer substitutional. When the same set of experiments were performed with As
as implantation ion all of the layers present diamagnetism without exception.
This indicates that the appearance of room-temperature ferromagnetic-like
behavior in the Mn-InAs-RTA layer is not related to lattice disorder produce
during implantation, but to a Mn reaction produced after a short thermal
treatment. X-ray diffraction patterns (XRD) and Rutherford Back Scattering
(RBS) measurements evidence the segregation of an oxygen deficient-MnO2 phase
(nominally MnO1.94) in the Mn-InAs-RTA epitaxial layers which might be on the
origin of room temperature ferromagnetic-like response observed.Comment: 16 pages, 5 figures. Acepted in J. Appl. Phy
Strangeness on the nucleon
Observables from parity violation in elastic electron-nucleon scattering and
neutral current quasi-elastic neutrino-nucleus scattering are employed as tools
to improve the current knowledge on the strangeness content in the nucleon.Comment: Proceedings of International Scientific Meeting on Nuclear Physics,
9-13th September 2012. La R\'abida, Huelva, Spai
Impact of Electric Fields on Highly Excited Rovibrational States of Polar Dimers
We study the effect of a strong static homogeneous electric field on the
highly excited rovibrational levels of the LiCs dimer in its electronic ground
state. Our full rovibrational investigation of the system includes the
interaction with the field due to the permanent electric dipole moment and the
polarizability of the molecule. We explore the evolution of the states next to
the dissociation threshold as the field strength is increased. The rotational
and vibrational dynamics are influenced by the field; effects such as
orientation, angular motion hybridization and squeezing of the vibrational
motion are demonstrated and analyzed. The field also induces avoided crossings
causing a strong mixing of the electrically dressed rovibrational states.
Importantly, we show how some of these highly excited levels can be shifted to
the continuum as the field strength is increased, and reversely how two atoms
in the continuum can be brought into a bound state by lowering the electric
field strength.Comment: 10 pages, 4 figure
Marginal Fermi liquid behavior from 2d Coulomb interaction
A full, nonperturbative renormalization group analysis of interacting
electrons in a graphite layer is performed, in order to investigate the
deviations from Fermi liquid theory that have been observed in the experimental
measures of a linear quasiparticle decay rate in graphite. The electrons are
coupled through Coulomb interactions, which remain unscreened due to the
semimetallic character of the layer. We show that the model flows towards the
noninteracting fixed-point for the whole range of couplings, with logarithmic
corrections which signal the marginal character of the interaction separating
Fermi liquid and non-Fermi liquid regimes.Comment: 7 pages, 2 Postscript figure
An explanation of the as a bound state
We use the interaction in the hidden gauge formalism to
dynamically generate and resonances. We show,
through a comparison of the results from this analysis and from a quark model
study with data, that the
and resonances can be assigned to bound
states. More precisely the can be interpreted as a
bound state whereas the and
may contain an important component. This
interpretation allows for a solution of a long-standing puzzle concerning the
description of these resonances in constituent quark models. In addition we
also obtain degenerate states but their
assignment to experimental resonances is more uncertain.Comment: 19 pags, 8 fig
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Composite polymer membranes for laserinduced fluorescence thermometry
We demonstrate a modified version of laser-induced fluorescence thermometry (LIFT) for mapping temperature gradients in the vicinity of small photothermal devices. Our approach is based on temperature sensitive fluorescent membranes fabricated with rhodamine B and polydimethylsiloxane (PDMS). Relevant membrane features for LIFT, such as temperature sensitivity, thermal quenching and photobleaching are presented for a range of 25 °C to 90 °C, and their performance is evaluated upon obtaining the temperature gradients produced in the proximity of optical fiber micro-heaters. Our results show that temperature measurements in regions as small as 750 Όm x 650 Όm, with a temperature resolution of 1 °C, can be readily obtained
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