705 research outputs found
Interaction-induced shift of the cyclotron resonance of graphene using infrared spectroscopy
We report a study of the cyclotron resonance (CR) transitions to and from the
unusual Landau level (LL) in monolayer graphene. Unexpectedly, we find
the CR transition energy exhibits large (up to 10%) and non-monotonic shifts as
a function of the LL filling factor, with the energy being largest at
half-filling of the level. The magnitude of these shifts, and their
magnetic field dependence, suggests that an interaction-enhanced energy gap
opens in the level at high magnetic fields. Such interaction effects
normally have limited impact on the CR due to Kohn's theorem [W. Kohn, Phys.
Rev. {\bf 123}, 1242 (1961)], which does not apply in graphene as a consequence
of the underlying linear band structure.Comment: 4 pages, 4 figures. Version 2, edited for publication. Includes a
number of edits for clarity; also added a paragraph contrasting our work w/
previous CR expts. in 2D Si and GaA
Supersymmetry Protects the Primordial Baryon Asymmetry
It has been argued that any primordial B+L asymmetry existing at very high
temperatures can be subsequently erased by anomalous electroweak effects. We
argue that this is not necessarily the case in the supersymmetric standard
model because, apart from B and/or L, there are, above a certain temperature
, two other anomalous U(1) currents. As a consequence, anomalous
electroweak effects are only able to partially transform a B+L excess into a
generation of primordial sparticle (e.g. gaugino) density. This relaxes recent
bounds on B,L-violating non-renormalizable couplings by several orders of
magnitude. In particular, dimension-5 couplings inducing neutrino masses may be
4 orders of magnitude larger than in the non-supersymmetric case, allowing for
neutrino masses of the order of 10 eV. These values are consistent with a
MSW+see-saw explanation of the solar-neutrino data and also with possible
neutrino oscillations measurable at accelerators. Cosmological bounds on other
rare processes, such as neutron-antineutron oscillations get also relaxed by
several orders of magnitude compared with previous estimates.Comment: (15 pages
A diagnostic challenge in an individual with Paracoccidioidomycosis during hospitalization in times of COVID-19
Paracoccidioidomycosis (PCM) is a deep fungal infection, endemic with considerable morbidity in South America, whose first symptoms can occur in the oral cavity. A 47-year-old male patient, leucoderma, living on the streets, presenting dyspnea, pain during the speech, and dysphagia, was referred for admission to the ICU for suspected COVID-19 infection. The intensive care physician\u27s evaluation revealed a tongue lesion with suspected carcinoma. By dentist investigation, was observed the presence of moriform lesions with high borders delimitation in the tongue. Also, granulomatous ulcers with irregular texture, suggesting moriform stomatitis, the chest tomography revealed diffuse thickening of the bronchial walls, indicating chronic bronchopathy with discrete centrilobular nodules, sometimes confluent. Incisional tongue biopsy associated with lung imaging confirmed the diagnosis of PCM, and the patient was referred to the referral center for the treatment of fungal diseases. The involvement of the oral environment as a region to the appearance of detectable first symptoms of PCM suggests the need for the oral evaluation by a specialist as a diagnostic tool
Applications for ultimate spatial resolution in LASER based -ARPES: A FeSe case study
Combining Angle resolved photoelectron spectroscopy (ARPES) and a
-focused Laser, we have performed scanning ARPES microscopy measurements
of the domain population within the nematic phase of FeSe single crystals. We
are able to demonstrate a variation of the domain population density on a scale
of a few 10 m while constraining the upper limit of the single domain size
to less than 5 . This experiment serves as a demonstration of how
combining the advantages of high resolution Laser ARPES and an ultimate control
over the spatial dimension can improve investigations of materials by reducing
the cross contamination of spectral features of different domains
Cyclotron motion in graphene
We investigate cyclotron motion in graphene monolayers considering both the
full quantum dynamics and its semiclassical limit reached at high carrier
energies. Effects of zitterbewegung due to the two dispersion branches of the
spectrum dominate the irregular quantum motion at low energies and are obtained
as a systematic correction to the semiclassical case. Recent experiments are
shown to operate in the semiclassical regime.Comment: 6 pages, 1 figure include
Searching for the MSW Enhancement
We point out that the length scale associated with the MSW effect is the
radius of the Earth. Therefore to verify matter enhancement of neutrino
oscillations, it will be necessary to study neutrinos passing through the
Earth. For the parameters of MSW solutions to the solar neutrino problem, the
only detectable effects occur in a narrow band of energies from 5 to 10 MeV. We
propose that serious consideration be given to mounting an experiment at a
location within 9.5 degrees of the equator.Comment: 10 pages, RevTe
Muon-Spin Rotation Measurements of the Magnetic Field Dependence of the Vortex-Core Radius and Magnetic Penetration Depth in NbSe2
Muon-spin rotation spectroscopy has been used to measure the internal
magnetic field distribution in NbSe2 for Hc1 << H < 0.25 Hc2. The deduced
profiles of the supercurrent density indicate that the vortex-core radius in
the bulk decreases sharply with increasing magnetic field. This effect, which
is attributed to increased vortex-vortex interactions, does not agree with the
dirty-limit microscopic theory. A simple phenomenological equation in which the
core radius depends on the intervortex spacing is used to model this behaviour.
In addition, we find for the first time that the in-plane magnetic penetration
depth increases linearly with H in the vortex state of a conventional
superconductor.Comment: 4 pages, RevTeX, 4 encapsulated postscript figures, (to appear in
Phys. Rev. Lett. 25Aug97 issue
Field-theoretical approach to particle oscillations in absorbing matter
The oscillations in absorbing matter are considered. The standard model
based on optical potential does not describe the total transition
probability as well as the channel corresponding to absorption of the
-particle. We calculate directly the off-diagonal matrix element in the
framework of field-theoretical approach. Contrary to one-particle model, the
final state absorption does not tend to suppress the channels mentioned above
or, similarly, calculation with hermitian Hamiltonian leads to increase the
corresponding values. The model reproduces all the results on the particle
oscillations, however it is oriented to the description of the above-mentioned
channels. Also we touch on the problem of infrared singularities. The approach
under study is infrared-free.Comment: 27 pages, 8 figure
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