Creation and dynamics of spin fluctuations in a noisy magnetic field

We theoretically and numerically investigate the spin fluctuations induced in a thermal atomic ensemble by an external fluctuating uniaxial magnetic field, in the context of a standard spin noise spectroscopy (SNS) experiment. We show that additional spin noise is excited, which dramatically depends on the magnetic noise variance and bandwidth, as well as on the power of the probe light and its polarization direction. We develop an analytical perturbative model proving that this spin noise first emerges from the residual optical pumping in the medium, which is then converted into spin fluctuations by the magnetic noise and eventually detected using SNS. The system studied is a spin-1 system, which thus shows both Faraday rotation and ellipticity noises induced by the random magnetic fluctuations. The analytical model gives results in perfect agreement with the numerical simulations, with potential applications in future experimental characterization of stray field properties and their influence on spin dynamics.Comment: 16 pages, 10 figures, submitted to New Journal of Physic

Molecularly Resolved Electronic Landscapes of Differing Acceptor-Donor Interface Geometries

Organic semiconductors are a promising class of materials for numerous electronic and optoelectronic applications, including solar cells. However, these materials tend to be extremely sensitive to the local environment and surrounding molecular geometry, causing the energy levels near boundaries and interfaces essential to device function to differ from those of the bulk. Scanning Tunneling Microscopy and Spectroscopy (STM/STS) has the ability to examine both the structural and electronic properties of these interfaces on the molecular and submolecular scale. Here we investigate the prototypical acceptor/donor system PTCDA/CuPc using sub-molecularly resolved pixel-by-pixel STS to demonstrate the importance of subtle changes in interface geometry in prototypical solar cell materials. PTCDA and CuPc were sequentially deposited on NaCl bilayers to create lateral heterojunctions that were decoupled from the underlying substrate. Donor and acceptor states were observed to shift in opposite directions suggesting an equilibrium charge transfer between the two. Narrowing of the gap energy compared to isolated molecules on the same surface are indicative of the influence of the local dielectric environment. Further, we find that the electronic state energies of both acceptor and donor are strongly dependent on the ratio and positioning of both molecules in larger clusters. This molecular-scale structural dependence of the electronic states of both interfacial acceptor and donor has significant implications for device design where level alignment strongly correlates to device performance

Selective Hybridization of a Terpyridine-Based Molecule with a Noble Metal

The electronic properties of metal-molecule interfaces can in principle be controlled by molecular design and self-assembly, yielding great potential for future nano- and optoelectronic technologies. However, the coupling between molecular orbitals and the electronic states of the surface can significantly influence molecular states. In particular, molecules designed to create metal-organic self-assembled networks have functional groups that by necessity are designed to interact strongly with metals. Here, we investigate the adsorption interactions of a terpyridine (tpy)-based molecule on a noble metal, Ag(111), by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) together with density functional theory (DFT) calculations. By comparing the local density of states (DOS) information gained from STS for the molecule on the bare Ag(111) surface with that of the molecule decoupled from the underlying metal by a NaCl bilayer, we find that tpy-localized orbitals hybridize strongly with the metal substrate. Meanwhile, those related to the phenyl rings that link the two terminal tpy groups are less influenced by the interaction with the surface. The selective hybridization of the tpy groups provides an example of strong, orbital-specific electronic coupling between a functional group and a noble-metal surface, which may alter the intended balance of interactions and resulting electronic behavior of the molecule-metal interface

Systematic and statistical uncertainty evaluation of the HfF+^+ electron electric dipole moment experiment

We have completed a new precision measurement of the electron's electric dipole moment using trapped HfF$^+$ in rotating bias fields. We report on the accuracy evaluation of this measurement, describing the mechanisms behind our systematic shifts. Our systematic uncertainty is reduced by a factor of 30 compared to the first generation of this measurement. Our combined statistical and systematic accuracy is improved by a factor of 2 relative to any previous measurement

A new bound on the electron's electric dipole moment

The Standard Model cannot explain the dominance of matter over anti-matter in our universe. This imbalance indicates undiscovered physics that violates combined CP symmetry. Many extensions to the Standard Model seek to explain the imbalance by predicting the existence of new particles. Vacuum fluctuations of the fields associated with these new particles can interact with known particles and make small modifications to their properties; for example, particles which violate CP symmetry will induce an electric dipole moment of the electron (eEDM). The size of the induced eEDM is dependent on the masses of the new particles and their coupling to the Standard Model. To date, no eEDM has been detected, but increasingly precise measurements probe new physics with higher masses and weaker couplings. Here we present the most precise measurement yet of the eEDM using electrons confined inside molecular ions, subjected to a huge intra-molecular electric field, and evolving coherently for up to 3 s. Our result is consistent with zero and improves on the previous best upper bound by a factor $\sim2.4$. Our sensitivity to $10^{-19}$ eV shifts in molecular ions provides constraints on broad classes of new physics above $10^{13}$ eV, well beyond the direct reach of the LHC or any other near- or medium-term particle collider.Comment: Update to figure 2 which displays better in some pdf viewer

Designing optoelectronic properties by on-surface synthesis: formation and electronic structure of an iron-terpyridine macromolecular complex

Supramolecular chemistry protocols applied on surfaces offer compelling avenues for atomic scale control over organic-inorganic interface structures. In this approach, adsorbate-surface interactions and two-dimensional confinement can lead to morphologies and properties that differ dramatically from those achieved via conventional synthetic approaches. Here, we describe the bottom-up, on-surface synthesis of one-dimensional coordination nanostructures based on an iron (Fe)-terpyridine (tpy) interaction borrowed from functional metal-organic complexes used in photovoltaic and catalytic applications. Thermally activated diffusion of sequentially deposited ligands and metal atoms, and intra-ligand conformational changes, lead to Fe-tpy coordination and formation of these nanochains. Low-temperature Scanning Tunneling Microscopy and Density Functional Theory were used to elucidate the atomic-scale morphology of the system, providing evidence of a linear tri-Fe linkage between facing, coplanar tpy groups. Scanning Tunneling Spectroscopy reveals highest occupied orbitals with dominant contributions from states located at the Fe node, and ligand states that mostly contribute to the lowest unoccupied orbitals. This electronic structure yields potential for hosting photo-induced metal-to-ligand charge transfer in the visible/near-infrared. The formation of this unusual tpy/tri-Fe/tpy coordination motif has not been observed for wet chemistry synthesis methods, and is mediated by the bottom-up on-surface approach used here

Advances in technologies for propagation and domestication of plants of economic and environmental interest in Argentina

En el Laboratorio de Estudios de la Madera de la Facultad de Ciencias Agrarias y Forestales de la Universidad Nacional de La Plata, Argentina, se implementa el proyecto de desarrollo tecnológico denominado Métodos y tecnologías de propagación y domesticación de plantas para el desarrollo de una bioeconomía local basada en la biodiversidad. El objetivo del mismo es desarrollar, optimizar y adaptar nuevas metodologías y tecnologías de propagación y conservación de recursos genéticos vegetales para la producción de plantas en nuevo escenario de la bioeconomía nacional. La diversidad está en la base de la bioeconomía, y muchas veces el material vegetal para plantar para diferentes fines es escaso. Las especies contempladas en éste proyecto son: Quercus sp.; Polylepis tarapacana; Prosopis alpataco, Eranthemun pulchelum y Heteropteris angustifolia Griseb. En este trabajo se comunican algunos de los avances alcanzados aplicando diferentes enfoques para la producción de plantas de calidad (semillas, cultivo de tejidos in vitro, macropropagación y plantines en contenedores).The Timber Research Laboratory of the Faculty of Agricultural and Forestry Sciences of the National University of La Plata (LIMAD), Argentina, implements the technological development project called Methods and technologies of plant propagation and domestication for the development of a local bioeconomy based on biodiversity. Its objective is to develop, optimize and adapt new methodologies and technologies for the propagation and conservation of plant genetic resources for the production of plants in a new scenario of national bioeconomy. Diversity is at the base of bioeconomy, and often planting plant material for different purposes is scarce. The species covered by this project are: Quercus sp. (exotic forest); Polylepis tarapacana (native forest); Prosopis alpataco. (multipurpose native forestry), Eranthemun pulchelum and Heteropteris angustifolia Griseb (ornamental species of great potential and use in green roofs). This work communicates some of the progress made by applying different approaches to the production of quality plants (seeds, in vitro tissue culture, macro propagation and seed container planting).Fil: Sharry, E.S.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Weber, C.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Cellini, M.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Lopez, Victoria Lien. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Boeri, P.. Universidad Nacional de Rio Negro. Sede Alto Valle y Valle Medio.; ArgentinaFil: Roussy, L.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Sceglio, P.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Ramilo, D.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Galarco, S.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentin