3,922 research outputs found
Wavepacket scattering on graphene edges in the presence of a (pseudo) magnetic field
The scattering of a Gaussian wavepacket in armchair and zigzag graphene edges
is theoretically investigated by numerically solving the time dependent
Schr\"odinger equation for the tight-binding model Hamiltonian. Our theory
allows to investigate scattering in reciprocal space, and depending on the type
of graphene edge we observe scattering within the same valley, or between
different valleys. In the presence of an external magnetic field, the well know
skipping orbits are observed. However, our results demonstrate that in the case
of a pseudo-magnetic field, induced by non-uniform strain, the scattering by an
armchair edge results in a non-propagating edge state.Comment: 8 pages, 7 figure
All-strain based valley filter in graphene nanoribbons using snake states
A pseudo-magnetic field kink can be realized along a graphene nanoribbon
using strain engineering. Electron transport along this kink is governed by
snake states that are characterized by a single propagation direction. Those
pseudo-magnetic fields point towards opposite directions in the K and K'
valleys, leading to valley polarized snake states. In a graphene nanoribbon
with armchair edges this effect results in a valley filter that is based only
on strain engineering. We discuss how to maximize this valley filtering by
adjusting the parameters that define the stress distribution along the graphene
ribbon.Comment: 8 pages, 6 figure
Efeito da interação entre níveis de irrigação e doses de potássio no crescimento do girassol EMBRAPA 122/V2000.
Influência de nitrogênio, micronutrientes e matéria orgânica na produção de melão.
O trabalho constituiu-se de dois experimentos com a cultura do melão (Cucumis melo L.) conduzidos em um Latossolo Vermelho-Amarelo, de textura arenosa no Campo Experimental de Bebedouro, em Petrolina-PE e em um Vertissolo, no Campo Experimental de Mandacaru, em Juazeiro-BA, ambos pertencentes a Embrapa Semi-Árido
Universal decay of scalar turbulence
The asymptotic decay of passive scalar fields is solved analytically for the
Kraichnan model, where the velocity has a short correlation time. At long
times, two universality classes are found, both characterized by a distribution
of the scalar -- generally non-Gaussian -- with global self-similar evolution
in time. Analogous behavior is found numerically with a more realistic flow
resulting from an inverse energy cascade.Comment: 4 pages, 3 Postscript figures, submitted to PR
First look with JWST spectroscopy: galaxies resemble local analogues
Deep images and near-IR spectra of galaxies in the field of the lensing
cluster SMACS J0723.3-7327 were recently taken in the Early Release
Observations program of JWST. Among these, two NIRSpec spectra of galaxies at
and one at were obtained, revealing for the first time
rest-frame optical emission line spectra of galaxies in the epoch of
reionization, including the detection of the important[OIII]4363 auroral line
(see JWST PR 2022-035). We present an analysis of the emission line properties
of these galaxies, finding that these galaxies have a high excitation (as
indicated by high ratios of [OIII]/[OII], [NeIII]/[OII]), strong
[OIII]4363/H, high equivalent widths, and other properties which are
typical of low-metallicity star-forming galaxies. Using the direct method we
determine oxygen abundances of in two galaxies, and
a lower metallicity of in the galaxy
using different strong line methods. More accurate metallicity determinations
will require better data. With stellar masses estimated from SED fits, we find
that the three galaxies lie close to or below the mass-metallicity
relation. Overall, these first galaxy spectra at show a strong
resemblance of the emission lines properties of galaxies in the epoch of
reionization with those of relatively rare local analogues previously studied
from the SDSS. Clearly, the first JWST observations demonstrate already the
incredible power of spectroscopy to reveal properties of galaxies in the early
Universe.Comment: 6 pages, 6 Figures. Accepted for publication in Astronomy &
Astrophysics Letter
Optical absorption of single-layer hexagonal boron nitride in the ultraviolet
In this paper we theoretically describe the absorption of hexagonal boron nitride (hBN) single layer. We develop the necessary formalism and present an efficient method for solving the Wannier equation for excitons. We give predictions for the absorption of hBN on quartz and on graphite. We compare our predictions with recently published results (Elias et al 2019 Nat. Commun. 10 2639) for a monolayer of hBN on graphite. The spontaneous radiative lifetime of excitons in hBN is also computed. We argue that the optical properties of hBN in the ultraviolet are very useful for the study of peptides and other biomolecules.The authors would like to thank André Chaves and Bruno Amorim for reading the manuscript, making suggestions, and for discussions on the topic of the paper. NMRP acknowledges support from the European Commission through the project 'Graphene-Driven Revolutions in ICT and Beyond' (Ref. No. 785219), and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2019. In addition, NMRP acknowledges COMPETE2020, PORTUGAL2020, FEDER and the Portuguese Foundation for Science and Technology (FCT) through projects PTDC/FIS- NAN/3668/2013 and POCI-01-0145-FEDER-028114, and POCI-01-0145-FEDER-029265 and PTDC/NAN-OPT/29265/2017, the authors also acknowledge the funding of Fundação da Ciência e Tecnologia, of COMPETE 2020 program in the FEDER component (European Union), through the project POCI-01-0145-FEDER-02888
Crescimento do girassol EMBRAPA 122/V-2000 submetido à adubação nitrogenada e lâminas de irrigação em um argissolo.
Transport properties of one-dimensional interacting fermions in aperiodic potentials
Motivated by the existence of metal-insulator transition in one-dimensional
non-interacting fermions in quasiperiodic and pseudorandom potentials, we
studied interacting spinless fermion models using exact many-body Lanczos
diagonalization techniques. Our main focus was to understand the effect of the
fermion-fermion interaction on the transport properties of aperiodic systems.
We calculated the ground state energy and the Kohn charge stiffness Dc. Our
numerical results indicate that there exists a region in the interaction
strength parameter space where the system may behave differently from the
metallic and insulating phases. This intermediate phase may be characterized by
a power law scaling of the charge stiffness constant in contrast to the
localized phase where Dc scales exponentially with the size of the system.Comment: 11 pages LaTex document with 5 eps figures. Uses revtex style file
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