Measurement of electron wave functions and confining potentials via photoemission

Wave functions and electron potentials of laterally confined surface states are determined experimentally by means of photoemission from stepped Au(111) surfaces. The confined nature of the wave function makes it possible to use an iterative formalism borrowed from x-ray diffraction where real-space wave functions are retrieved from the absolute values of their Fourier transforms. The latter are measured by angle-resolved photoemission. The effective confining potential is then obtained by introducing the wave functions into Schrödinger’s equation.A.M. and J.E.O. are supported by the Universidad del Pais Vasco Grant No. 9/UPV 00057.240-13668/2001 and the Max Planck Research Institute. J.G.A. gratefully acknowledges support by the Basque Departamento de Educacion, Universidades e Investigacion, the University of the Basque Country UPV/EHU Contract No. 00206.215-13639/2001, and the Spanish Ministerio de Ciencia y Tecnologia Contract No. MAT2001-0946. F.J.H. acknowledges support by the NSF under Grants Nos. DMR-9815416 and DMR0084402.Peer reviewe

Diacritical study of light, electrons, and sound scattering by particles and holes

We discuss the differences and similarities in the interaction of scalar and vector wave-fields with particles and holes. Analytical results are provided for the transmission of isolated and arrayed small holes as well as surface modes in hole arrays for light, electrons, and sound. In contrast to the optical case, small-hole arrays in perforated perfect screens cannot produce acoustic or electronic surface-bound states. However, unlike electrons and light, sound is transmitted through individual holes approximately in proportion to their area, regardless their size. We discuss these issues with a systematic analysis that allows exploring both common properties and unique behavior in wave phenomena for different material realizations.Comment: 3 figure

Excitation of confined modes on particle arrays

We describe both theoretically and experimentally the existence and excitation of confined modes in planar arrays of gold nanodisks. Ordered 2D lattices of monodispersive nanoparticles are manufactured, embedded in a silica matrix, and exposed to evanescent prism-coupling illumination, leading to dark features in the reflectivity, which signal the presence of confined modes guided along the arrays. We find remarkable agreement between theory and experiment in the frequency-momentum dispersion of the resonances. Direct excitation of these modes reveals long propagation distances and deep extinction features. This combined experimental and theoretical characterization of guidedmodes shows a good understanding of the optical response of metallic particles arrays, which can be beneficial in future designs of optical-signal and distant-sensing applications. © 2013 Optical Society of America.This work has been supported in part by the European Union (NMP4-2006-016881-SPANS, NMP4-SL-2008-213669-ENSEMBLE,FP7-ICT-2009-4-248909-LIMA, and FP7-ICT-2009-4-248855-N4E), the Spanish MEC (MAT2010-14885 and Consolider Nano-Light.es), and the research program of the Foundation for Fundamental Research on Matter (FOM), which is financially supported by the Netherlands Organization for Fundamental Research (NWO) and is part of an industrial partnership program between Philips and FOM. It is also supported in part by NanoNextNL, a micro and nanotechnology consortium of the Government of the Netherlands and 130 partners. X.M.B. acknowledges a Spanish CSIC-JAE grant.Peer Reviewe

Ultraefficient Coupling of a Quantum Emitter to the Tunable Guided Plasmons of a Carbon Nanotube

We show that a single quantum emitter can efficiently couple to the tunable plasmons of a highly doped single-wall carbon nanotube (SWCNT). Plasmons in these quasi-one-dimensional carbon structures exhibit deep subwavelength confinement that pushes the coupling efficiency close to 100% over a very broad spectral range. This phenomenon takes place for distances and tube diameters comprising the nanometer and micrometer scales. In particular, we find a β factor ≈1 for QEs placed 1–100 nm away from SWCNTs that are just a few nanometers in diameter, while the corresponding Purcell factor exceeds 106.Postprint (published version

Impact of pre-exposure time bias in self-controlled case series when the event conditions the exposure: Hip/femur fracture and use of benzodiazepines as a case study.

BACKGROUND: In self-controlled case series (SCCS), the event should not condition the probability of subsequent exposure. If this assumption is not met, an important bias could take place. The association of hip/femur fracture (HFF) and use of benzodiazepines (BDZ) has a bidirectional causal relationship and can serve as case study to investigate the impact of this methodological issue. OBJECTIVES: To assess the magnitude of bias introduced in a SCCS when HFF conditions the posterior exposure to BDZ and explore ways to correct it. METHODS: Four thousand four hundred fifty cases of HFF who had at least one BZD prescription were selected from the primary care health record database BIFAP. Exposure to BZD was divided into non-use, current, recent, and past use. Conditional Poisson regression was used to estimate incidence rate ratios (IRRs) of HFF among current vs non-use/past, adjusted for age. To investigate possible event-exposure dependence, a pre-exposure time of different lengths (15, 30, and 60 days) was excluded from the reference category to evaluate the IRR. RESULTS: IRR of HHF for current use was 0.79 (0.72-0.86); removing 30 days, IRR was 1.43 (1.31-1.57). Removing 15 days, IRR was 1.29 (1.18-1.41), and removing 60 days, IRR was 1.56 (1.42-1.72). A pre-exposure period up to 182 days was necessary to remove such effect giving an IRR of 1.64 (1.48-1.81). CONCLUSIONS: HFF remarkably conditioned the use of BDZs resulting in seriously biased IRRs when this association was studied through a SCCS design. The use of pre-exposure periods of different lengths helped to correct this error

Plasmon wave function of graphene nanoribbons

We find the low-frequency optical response of highly doped individual and arrayed graphene nanoribbons to be accurately described in terms of plasmon wave functions (PWFs). More precisely, we focus on the lowest-order transverse dipolar mode, for which we define the wave function as the induced charge density associated with the plasmon. We show that a single universal wave function is capable of describing the normal-incidence interaction of paired, co-planar, and stacked arrays of ribbons down to small inter-ribbon distances. Our work provides both intuitive insight into graphene plasmon interactions and a practical way of accurately describing complex graphene geometries based on the PWFs of the individual components.Peer ReviewedPostprint (published version

Accurate band mapping via photoemission from thin films

Electron bands in solids can be determined in angle-resolved photoemission experiments from thin films, where the perpendicular wave vector (k⊥) uncertainty that characterizes photoemission from bulk crystals is removed. However, the comparison with state-of-the-art quasiparticle band-structure calculations has never been done. In this work we have mapped both initial-state (occupied) and final-state (empty) E(k⊥) bands along the A axis of aluminum, from photon-energy- and thickness-dependent quantum-well spectra of aluminum films. For final states the best fit is obtained with inverse low-energy electron diffraction band structure calculations. For initial-state bands of Cu and Al, thin-film data display excellent agreement with bulk quasiparticle theory, suggesting the use of thin films as model systems to investigate fine effects in the crystal band structure.This work has been supported in part by the Universidad del País Vasco (A.Mu. and J.E.O. under Contract No. 00057.240-EA-13668/2001, and A.Ma., A.R., and F.J.G.A. under Contract No. 00206.215-13639/2001), the European Community (EC) research training network NANOPHASE [A.Ma. and A.R. (Grant No. HPRN-CT-2000-00167)], and the Spanish Ministerio de Ciencia y Tecnología [A.Ma., A.R., and F.J.G.A. (Grant No. MAT2001-0946), and J.L. and E.G.M. (BFM2001-0244)].Peer Reviewe

Utilización de ansiolíticos e hipnóticos en España (1995-2002)

Producción CientíficaFundamento: Estudios recientes han señalado un aumento en el consumo de ansiolíticos e hipnóticos, así como su uso inadecuado, en países occidentales. El objetivo de este trabajo es conocer su patrón de utilización en España entre los años 1995 y 2002. Métodos: Los datos de consumo de medicamentos se obtuvieron de la base de datos ECOM (Especialidades Consumo de Medicamentos) del Ministerio de Sanidad y Consumo, que contiene información sobre el consumo de medicamentos dispensados con cargo al Sistema Nacional de Salud en farmacias comunitarias. Los datos se expresaron en Dosis Diarias Definidas por 1.000 habitantes y día. Resultados: La utilización de ansiolíticos e hipnóticos creció desde 39,71 Dosis Diarias Definidas por 1.000 habitantes y día en 1995 a 62,02 en 2002. A lo largo del periodo estudiado las benzodiazepinas de vida media intermedia (8-24 horas) fueron los medicamentos más utilizados, en especial lorazepam, alprazolam y lormetazepam. El principio activo que más disminuyó su consumo fue el flunitrazepam. Conclusiones: Aunque el consumo de ansiolíticos e hipnóticos en España experimentó un notable incremento en los últimos años, el patrón de consumo no presentó modificaciones sustanciales