131 research outputs found
Strong competition between -loop-current order and -wave charge order along the diagonal direction in a two-dimensional hot spot model
We study the fate of the so-called -loop-current order that
breaks both time-reversal and parity symmetries in a two-dimensional hot spot
model with antiferromagnetically mediated interactions, using Fermi surfaces
relevant to the phenomenology of the cuprate superconductors. We start from a
three-band Emery model describing the hopping of holes in the CuO plane
that includes two hopping parameters and , local on-site
Coulomb interactions and and nearest-neighbor
couplings between the fermions in the copper [Cu] and
oxygen [O and O] orbitals. By focusing on the lowest-energy
band, we proceed to decouple the local interaction of the Cu orbital in
the spin channel using a Hubbard-Stratonovich transformation to arrive at the
interacting part of the so-called spin-fermion model. We also decouple the
nearest-neighbor interaction to introduce the order parameter of the
-loop-current order. In this way, we are able to construct a
consistent mean-field theory that describes the strong competition between the
composite order parameter made of a quadrupole-density-wave and -wave
pairing fluctuations proposed in Efetov \emph{et al.} [Nat. Phys. \textbf{9},
442 (2013)] with the -loop-current order parameter that is argued
to be relevant for explaining important aspects of the physics of the pseudogap
phase displayed in the underdoped cuprates.Comment: 16 pages, 5 figures. v2: minor revisions, references added. The
magnetic moment per unit-cell associated with the
-loop-current-phase is calculated and compared with experimental
results. Accepted for publication in Physical Review
Electronic spectral function in fractionalized Pair Density Wave scenario
Studies of the electronic spectral function in cuprates by Angle-Resolved
Photo-Emission Spectroscopy reveal unusual features in the pseudogap phase that
persist in the superconducting phase. We address here these observations based
on the recently proposed idea that the pseudogap is due to the
fractionalization of modulated particle-particle pairs (a Pair Density Wave)
into uniform particle-particle and modulated particle-hole pairs. The
constraint that appears between these two types of pairs can be seen has an
amplitude for the pseudogap energy scale. This constraint directly modify the
electronic spectral function in the pseudogap phase. We derive a
self-consistent equation for the pseudogap amplitude and show that it leads to
the formation of Fermi arcs. The band dispersion obtained in the anti-nodal
region is in good agreement with experimental ARPES observations in
PbBiSrLaCuO (Bi2201) and present
a back-bending that goes to the Fermi level as we go away from the antinodal
region. We also discuss the temperature dependence of the ARPES spectrum in the
pseudogap and in the superconducting state
Sostenibilidad energética y viabilidad monetaria de los cultivos herbáceos extensivos ecológico en Andalucía
Una de las características más importantes de la agricultura es su capacidad para transformar la energía y generar “excedentes” energéticos con diversos usos (alimentación humana, animal, fertilización, etc.). Estos excedentes energéticos son potencialmente mayores en la agricultura ecológica como resultado del menor uso de insumos vinculados a la energía fósil. Los cereales y las leguminosas son cultivos que se caracterizan por altos outputs y balances de energía, ambos indicadores fundamentales de la sostenibilidad agraria. En este trabajo se analiza, tanto en términos monetarios como energéticos, el comportamiento de los cultivos extensivos ecológicos en Andalucía para el año 2005. Así mismo, se realiza un análisis comparativo entre los resultados energéticos obtenidos en el presente estudio y los aportados en otros estudios nacionales e internacionales. El balance monetario y energético de los cultivos extensivos se estimó en 2,47 y 3,65 respectivamente. Este último se incrementa hasta 6,49 si solamente se tiene en cuenta el uso de energía no renovable. En términos comparativos con cultivos convencionales, los resultados muestran un elevado grado de eficiencia energética
Energy sustainability and economic viability of organic extensive herbaceous crops in Andalusia
Una de las características más importantes de la agricultura es su capacidad para transformar la energía y generar “excedentes” energéticos con diversos usos (alimentación humana, animal, fertilización, etc.). Estos
excedentes energéticos son potencialmente mayores en la agricultura ecológica como resultado del menor uso de insumos vinculados a la energía fósil. Los cereales y las leguminosas son cultivos que se caracterizan por
altos outputs y balances de energía, ambos indicadores fundamentales de la sostenibilidad agraria. En este trabajo se analiza, tanto en términos monetarios como energéticos, el comportamiento de los cultivos extensivos
ecológicos en Andalucía para el año 2005. Así mismo, se realiza un análisis comparativo entre los resultados energéticos obtenidos en el presente estudio y los aportados en otros estudios nacionales e internacionales. El
balance monetario y energético de los cultivos extensivos se estimó en 2,47 y 3,65 respectivamente. Este último se incrementa hasta 6,49 si solamente se tiene en cuenta el uso de energía no renovable. En términos comparativos con cultivos convencionales, los resultados muestran un elevado grado de eficiencia energética.One of the most important characteristics of agriculture is its capacity to transform energy and generate energy “surpluses” with various uses (human food, animal feed, fertilization, etc.). These energy surpluses are potentially larger in ecological agriculture as result of low fossil fuel inputs related. Cereals and legumes are crops with high energy balance and output, both key agrarian sustainability indicators. This work analyses the behaviour of ecological extensive crops in Andalusia (2005), in both monetary and energy terms. In addition, a comparative analysis is made of the energy results obtained in the present study and those contributed by other national and international studies. The monetary and energy balance of extensive crops is estimated at 2.47 and 3.65, respectively. When only the use of non-renewable energy is taken into consideration, the energy balance increases and reaches 6.49. In comparative terms, the results show a high degree of energy efficiency
Generation of pure superconducting spin current in magnetic heterostructures via nonlocally induced magnetism due to Landau Fermi liquid effects
We propose a mechanism for the generation of pure superconducting
spin-current carried by equal-spin triplet Cooper pairs in a superconductor (S)
sandwiched between a ferromagnet (F) and a normal metal (N) with
intrinsic spin-orbit coupling. We show that in the presence of Landau
Fermi-liquid interactions the superconducting proximity effect can induce
non-locally a ferromagnetic exchange field in the normal layer, which
disappears above the superconducting transition temperature of the structure.
The internal Landau Fermi-liquid exchange field leads to the onset of a spin
supercurrent associated with the generation of long-range spin-triplet
superconducting correlations in the trilayer. We demonstrate that the magnitude
of the spin supercurrent as well as the induced magnetic order in the N layer depends critically on the superconducting proximity effect between
the S layer and the F and N layers and the magnitude of the relevant
Landau Fermi-liquid interaction parameter. We investigate the effect of spin
flip processes on this mechanism. Our results demonstrate the crucial role of
Landau Fermi-liquid interaction in combination with spin-orbit coupling for the
creation of spin supercurrent in superconducting spintronics, and give a
possible explanation of a recent experiment utilizing spin-pumping via
ferromagnetic resonance [Jeon , Nat. Mat. , 499
(2018)]
Economía Ecológica y Ecología Política en el Ámbito de la Educación Ambiental
La crisis social y ambiental es uno de los mayores problemas al que se enfrentan las sociedades a día de hoy. Uno de los retos más importantes de la educación es dotar al profesorado y al alumnado de las herramientas conceptuales adecuadas para comprender y analizar la situación actual desde una perspectiva compleja. La economía ecológica y la ecología política forman parte de ese nuevo paradigma en construcción: el de la complejidad. A su vez, los indicadores biofísicos utilizados en economía ecológica pueden constituir buenas herramientas pedagógicas, analíticas y discursivas dentro de la educación ambiental, sobre todo dentro del marco analítico que nos ofrece la ecología política
EL DERECHO HUMANO DE ASOCIACIÓN Y SU VULNERACIÓN POR LA SOCIEDAD POR ACCIONES SIMPLIFICADAS (SAS)
This study will establish the basics of Human Rights in general terms, thereafter will focus analyzing exclusively the human right called of Association included in the Mexican Constitution and international treaties that Mexico has ratified. Once the subject matter as to the Association Right has been settled, will review the relatively new type of company called “Simplified Stock Company” (SSC), introduced in our General Company Law since the amendment published in the Federal Official Gazette on March 14, 2016, within its analysis we will focus on its distinguishing characteristics, thereafter, will identify and provide legal basis on how the Human Right called Association would be infringed when applying some institutions included in the SSC, in our conclusion will provide the available control methods as to the safeguard of the association right.En el presente estudio pretendemos establecer las bases de los derechos humanos en general, para posteriormente avocarnos al análisis exclusivo del derecho humano denominado de Asociación contenido en la Constitución Política de los Estados Unidos Mexicanos y los tratados internacionales de que México forma parte. Una vez establecido el campo de aplicación del Derecho de Asociación, y sus restricciones, se procederá al estudio general de las sociedades mercantiles en México, para en forma seguida analizar el relativamente nuevo tipo social denominado “Sociedad por Acciones Simplificada” (SAS), que fue introducido en nuestra Ley General de Sociedades Mercantiles a partir de la reforma publicada en el Diario Oficial de la Federación el día 14 de marzo de 2016, dentro del estudio de esta figura jurídica, haremos énfasis en sus peculiares características, para posteriormente determinar y fundamentar que disposiciones de la SAS vulnerarían el Derecho Humano de Asociación, para finalizar estableciendo los medios de control que pueden ser utilizados para salvaguardar el derecho de asociación
Spin-orbit coupling suppression and singlet-state blocking of spin-triplet Cooper pairs
An inhomogeneous magnetic exchange field at a superconductor/ferromagnet interface converts spin-singlet Cooper pairs to a spin-aligned (i.e. spin-polarized) triplet state. Although the decay envelope of such triplet pairs within ferromagnetic materials is well studied, little is known about their decay in non-magnetic metals and superconductors, and in particular in the presence of spin-orbit coupling (SOC). Here we investigate devices in which triplet supercurrents are injected into the s-wave superconductor Nb. In the normal state of Nb, triplet supercurrents decay over a distance of 5 nm, which is an order of magnitude smaller than the decay of spin singlet pairs due to the SOC interacting with the spin associated with triplet pairs. In the superconducting state of Nb, triplet supercurrents are not able to couple with the singlet wavefunction and thus blocked by the absence of available equilibrium states in the singlet gap. The results offer new insight into the dynamics between s-wave singlet and s-wave triplet states.S.K., J.M.D-S., G.Y., X.M., L.F.C., H.K., M.G.B., and J.W.A.R. acknowledge funding from the EPSRC Programme Grant “Superspin” (no. EP/N017242/1) and EPSRC International Network Grant “Oxide Superspin” (no. EP/P026311/1). K.O. acknowledges the JSPS Programme “Fostering Globally Talented Researchers” (JPMXS05R2900005). S.M. and A.I.B. acknowledge funding from Russian Science Foundation (grant no. 20-12-00053, in part related to the theoretical calculations). Zh.D. and S.M. acknowledge financial support from the Foundation for the advancement of theoretical physics “BASIS.” S.M. acknowledges financial support from the Russian Presidential Scholarship (SP-3938.2018.5
Atrial Fibrillation Originating in the Inferior Vena Cava
Recurrence of atrial fibrillation (AF) despite successful isolation of the pulmonary veins (PVs) represents a great challenge. We present a patient with recurrent episodes of paroxysmal AF despite PV isolation in which a non-PV trigger was identified in the inferior vena cava. (Level of Difficulty: Intermediate.
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