Magnon spin Hall magnetoresistance of a gapped quantum paramagnet

Motivated by recent experimental work, we consider spin transport between a normal metal and a gapped quantum paramagnet. We model the latter as the magnonic Mott-insulating phase of an easy-plane ferromagnetic insulator. We evaluate the spin current mediated by the interface exchange coupling between the ferromagnet and the adjacent normal metal. For the strongly interacting magnons that we consider, this spin current gives rise to a spin Hall magnetoresistance that strongly depends on the magnitude of the magnetic field, rather than its direction. This Letter may motivate electrical detection of the phases of quantum magnets and the incorporation of such materials into spintronic devices.Comment: 5 pages, 5 figure

Magnon-Mediated Indirect Exciton Condensation through Antiferromagnetic Insulators

Electrons and holes residing on the opposing sides of an insulating barrier and experiencing an attractive Coulomb interaction can spontaneously form a coherent state known as an indirect exciton condensate. We study a trilayer system where the barrier is an antiferromagnetic insulator. The electrons and holes here additionally interact via interfacial coupling to the antiferromagnetic magnons. We show that by employing magnetically uncompensated interfaces, we can design the magnon-mediated interaction to be attractive or repulsive by varying the thickness of the antiferromagnetic insulator by a single atomic layer. We derive an analytical expression for the critical temperature $T_c$ of the indirect exciton condensation. Within our model, anisotropy is found to be crucial for achieving a finite $T_c$, which increases with the strength of the exchange interaction in the antiferromagnetic bulk. For realistic material parameters, we estimate $T_c$ to be around 7 K, the same order of magnitude as the current experimentally achievable exciton condensation where the attraction is solely due to the Coulomb interaction. The magnon-mediated interaction is expected to cooperate with the Coulomb interaction for condensation of indirect excitons, thereby providing a means to significantly increase the exciton condensation temperature range.Comment: 7+13 Pages, 2+1 figures. Added discussion of retardation effects. Accepted for publication in Phys. Rev. Let

Agricultural productivity in the United States: catching-up and the business cycle

This paper examines the relation between the business cycle and convergence in levels of total factor productivity (TFP) across states. First, we find evidence of convergence in TFP levels across the different phases of the business cycle, but the speed of convergence was much greater during periods of contraction in economic activity than during periods of expansion. Second, we find that technology embodied in capital was an important source of productivity growth in agriculture. As with the rate of catch-up, the embodiment effect was much stronger during low economic activity phases of the business cycle.Agriculture, Convergence, Total factor productivity

Nonlocal Spin Transport as a Probe of Viscous Magnon Fluids

Magnons in ferromagnets behave as a viscous fluid over a length scale, the momentum-relaxation length, below which momentum-conserving scattering processes dominate. We show theoretically that in this hydrodynamic regime viscous effects lead to a sign change in the magnon chemical potential, which can be detected as a sign change in the nonlocal resistance measured in spin transport experiments. This sign change is observable when the injector-detector distance becomes comparable to the momentum-relaxation length. Taking into account momentum- and spin-relaxation processes, we consider the quasiconservation laws for momentum and spin in a magnon fluid. The resulting equations are solved for nonlocal spin transport devices in which spin is injected and detected via metallic leads. Because of the finite viscosity we also find a backflow of magnons close to the injector lead. Our work shows that nonlocal magnon spin transport devices are an attractive platform to develop and study magnon-fluid dynamics

Los efectos del tipo de cambio en la actividad y los precios del área del euro

Artículo de revist

Agricultural productivity in the United States: catching-up and the business cycle

This paper examines the relation between the business cycle and convergence in levels of total factor productivity (TFP) across states. First, we find evidence of convergence in TFP levels across the different phases of the business cycle, but the speed of convergence was much greater during periods of contraction in economic activity than during periods of expansion. Second, we find that technology embodied in capital was an important source of productivity growth in agriculture. As with the rate of catch-up, the embodiment effect was much stronger during low economic activity phases of the business cycle

Finite time extinction for nonlinear fractional evolution equations and related properties

The finite time extinction phenomenon (the solution reaches an equilibrium after a finite time) is peculiar to certain nonlinear problems whose solutions exhibit an asymptotic behavior entirely different from the typical behavior of solutions associated to linear problems. The main goal of this work is twofold. Firstly, we extend some of the results known in the literature to the case in which the ordinary time derivative is considered jointly with a fractional time differentiation. Secondly, we consider the limit case when only the fractional derivative remains. The latter is the most extraordinary case, since we prove that the finite time extinction phenomenon still appears, even with a non-smooth profile near the extinction time. Some concrete examples of quasi-linear partial differential operators are proposed. Our results can also be applied in the framework of suitable nonlinear Volterra integro-differential equations

Aspectos generales de la metodología para el cálculo del Margen Bruto Estándar 2000

El objetivo de este documento de trabajo es presentar la metodología para el cálculo del Margen Bruto Estándar con periodo de referencia 1999, 2000 y 2001 (MBE 2000) y para el conjunto de categorías agrícolas definidas en el anexo de la Decisión de la Comisión 2003/369/CE. En este documento, dichas categorías vienen recogidas en el cuadro 2 del anexo. Este documento de trabajo se divide en tres secciones. En la sección 1 se presenta el marco metodológico general recogido en la legislación comunitaria, prestando especial interés a la definición de MBE. Las secciones 2 y 3 presentan, de forma resumida, la metodología seguida para el cálculo de los coeficientes MBE 2000 de las categorías de cultivos y ganados respectivamente

Structural sensitivity of the spin Hall magnetoresistance in antiferromagnetic thin films

Reading the magnetic state of antiferromagnetic (AFM) thin films is key for AFM spintronic devices. We investigate the underlying physics behind the spin Hall magnetoresistance (SMR) of bilayers of platinum and insulating AFM hematite ({\alpha}-Fe2O3) and report a record SMR efficiency of up to ~1%. To understand the SMR field dependence, we analyse the role of the imaginary Néel spin-mixing conductance and find it key for the SMR response of uncompensated AFM interfaces. We demonstrate that the combined real and imaginary conductances can be used as a unique tool to unambiguously determine AFM textures

Measuring retail trade using card transactional data

En este trabajo se presenta un Índice de Comercio Minorista (ICM) de alta dimensionalidad construido para España, estimado a partir del uso de datos masivos. La información utilizada se corresponde con la que surge de las transacciones con tarjetas de crédito y de débito de los clientes de BBVA en terminales de punto de venta (TPV) españoles. Los índices obtenidos son robustos cuando se comparan con los que publica el Instituto Nacional de Estadística (INE), tanto para el conjunto de España como para las distintas regiones y los diferentes canales de distribución. Dando un paso más, se calculan los índices mensuales por provincias y por sectores (información no publicada por el INE) y se construye un índice general diario. A partir de este último índice, se analizan además las pautas de consumo en alta frecuencia a través de un modelo estructural de series temporalesIn this paper we present a high-dimensionality Retail Trade Index (RTI) constructed to nowcast the retail trade sector economic performance in Spain, using Big Data sources and techniques. The data are the footprints of BBVA clients from their credit or debit card transactions at Spanish point of sale (PoS) terminals. The resulting indexes have been found to be robust when compared with the Spanish RTI, regional RTI (Spain’s autonomous regions), and RTI by retailer type (distribution classes) published by the National Statistics Institute (INE). We also went one step further, computing the monthly indexes for the provinces and sectors of activity and the daily general index, by obtaining timely, detailed information on retail sales. Finally, we analyzed the high-frequency consumption dynamics using BBVA retailer behavior and a structural time series mode