Tunneling spectra of layered strongly correlated d-wave superconductors

Tunneling conductance experiments on cuprate superconductors exhibit a large diversity of spectra that appear in different nano-sized regions of inhomogeneous samples. In this letter, we use a mean-field approach to the tt't''J model in order to address the features in these spectra that deviate from the BCS paradigm, namely, the bias sign asymmetry at high bias, the generic lack of evidence for the Van Hove singularity, and the occasional absence of coherence peaks. We conclude that these features can be reproduced in homogeneous layered d-wave superconductors solely due to a proximate Mott insulating transition. We also establish the connection between the above tunneling spectral features and the strong renormalization of the electron dispersion around (0,pi) and (pi,0) and the momentum space anisotropy of electronic states observed in ARPES experiments.Comment: 4 pages, 3 figures. Added comment on the role of sample inhomogeneity. Published version. Homepage http://dao.mit.edu/~wen

Fruticultura tropical: uma alternativa para a agricultura de Rondônia.

Esta publicação apresenta a fruticultura como atividade econômica para o Estado de Rondônia. Traz informações técnicas sobre 6 fruteiras: Mangostãozeiro; Rambutanzeiro; Cupuaçuzeiro; Pupunheira; Açaizeiro; Araçá-boi; Camu-camu.bitstream/CPAF-RO-2010/14322/1/doc109-fruteirastropicais.pd

Nuclear State Preparation via Landau-Zener-Stueckelberg transitions in Double Quantum Dots

We theoretically model a nuclear-state preparation scheme that increases the coherence time of a two-spin qubit in a double quantum dot. The two-electron system is tuned repeatedly across a singlet-triplet level-anticrossing with alternating slow and rapid sweeps of an external bias voltage. Using a Landau-Zener-Stueckelberg model, we find that in addition to a small nuclear polarization that weakly affects the electron spin coherence, the slow sweeps are only partially adiabatic and lead to a weak nuclear spin measurement and a nuclear-state narrowing which prolongs the electron spin coherence. This resolves some open problems brought up by a recent experiment [D. J. Reilly et al., Science 321, 817 (2008).]. Based on our description of the weak measurement, we simulate a system with up to n=200 nuclear spins per dot. Scaling in n indicates a stronger effect for larger n.Comment: 4.1 pages, 2 figure

Rehybridization of electronic structure in compressed two-dimensional quantum dot superlattices

Two-dimensional superlattices of organically passivated 2.6-nm silver quantum dots were prepared as Langmuir monolayers and transferred to highly oriented pyrolytic graphite substrates. The structural and electronic properties of the films were probed with variable temperature scanning tunneling microscopy. Particles passivated with decanethiol (interparticle separation distance of ∼1.1±0.2 nm) exhibited Coulomb blockade and staircase. For particles passivated with hexanethiol or pentanethiol (interparticle separation distance of ∼0.5±0.2 nm), the single-electron charging was quenched, and the redistribution of the density of states revealed that strong quantum mechanical exchange, i.e., wave-function hybridization, existed among the particles in these films

Caracterização biometrica de frutos e sementes de matrizes de pracaxi (Pentaclethara macroloba - Wild).

P. macroloba (Fabaceae), conhecida popularmente como Pracaxi, é muito requisitada no mercado de óleos. Foram avaliados 50 frutos de cada uma das quatro matrizes, avaliando-se as seguintes variáveis dos frutos: massa, comprimento, largura, espessura, número total de sementes, número de sementes boas, número de sementes chochas e número de sementes danificadas por insetos. Nas sementes boas, avaliou-se a massa, comprimento, largura e espessura. As medias foram comparadas pelo teste de Tukey ao nível de 5% de probabilidade. Os frutos das quatro matrizes apresentaram massa fresca variando de 76,2 a 89,2g, comprimento de 318,2 a 385,5mm, largura de 41,5 a 46,2mm e espessura de 12,6 a 14,2mm, apresentando em media de 3,18 a 4,36 sementes, sendo de 2,35 a 3,74 sementes boas. As sementes apresentaram massa variando de 4,80 a 6,62g, comprimento de 39,95 a 43,81mm, largura de 27,60 a 31,02mm e espessura de 7,36 a 9,43mm. No geral, a matriz 482 apresentou os melhores resultados com relação à caracterização das sementes, enquanto que a matriz 515 obteve os maiores frutos

Multifractal Omori law for earthquake triggering: new tests on the California, Japan and worldwide catalogues

The Multifractal Stress-Activated model is a statistical model of triggered seismicity based on mechanical and thermodynamic principles. It predicts that, above a triggering magnitude cut-off M0, the exponent p of the Omori law for the time decay of the rate of aftershocks is a linear increasing function p(M) = a0M+b0 of the main shock magnitude M. We previously reported empirical support for this prediction, using the Southern California Earthquake Center (SCEC) catalogue. Here, we confirm this observation using an updated, longer version of the same catalogue, as well as new methods to estimate p. One of this methods is the newly defined Scaling Function Analysis (SFA), adapted from the wavelet transform. This method is able to measure a mathematical singularity (hence a p-value), erasing the possible regular part of a time-series. The SFA also proves particularly efficient to reveal the coexistence and superposition of several types of relaxation laws (typical Omori sequences and short-lived swarms sequences) which can be mixed within the same catalogue. Another new method consists in monitoring the largest aftershock magnitude observed in successive time intervals, and thus shortcuts the problem of missing events with small magnitudes in aftershock catalogues. The same methods are used on data from the worldwide Harvard Centroid Moment Tensor (CMT) catalogue and show results compatible with those of Southern California. For the Japan Meteorological Agency (JMA) catalogue, we still observe a linear dependence of p on M, but with a smaller slope. The SFA shows however that results for this catalogue may be biased by numerous swarm sequences, despite our efforts to remove them before the analysi

Coleção de fruteiras tropicais da Embrapa Rondônia.

O trabalho descreve as espécies vegetais existentes no Campo Experimental de Porto Velho da Embrapa Rondônia. A coleção de fruteiras tropicais da Embrapa Rondônia é enriquecida com variedades e acessos obtidos durante as expedições para coleta de material botânico e tem como objetivos as seguintes atividades: coleta e intercâmbio de material botânico, contribuindo para a conservação e enriquecimento dos bancos e coleções de germoplasma de espécies frutíferas nativas da Amazônia, manutenção e avaliação da coleção, além de efetuar a caracterização de acessos.bitstream/item/24673/1/cot306-fruteirastropicais.pd