Test Experiment for Time-Reversal Symmetry Breaking Superconductivity

A new experiment is proposed to probe the time-reversal symmetry of a superconductor. It is shown that a time-reversal symmetry breaking superconductor can be identified by the observation of a fractional flux in connection with a Josephson junction in a special geometry.Comment: 4 pages, 2 figures available upon request, Revtex, MIT-CMT-OC

What if? Policy analysis with calibrated equilibrium models

The goal of this paper is to build up and apply a simple static model of world oil markets.CGE, static model, oil markets

Checkerboard order in the t--J model on the square lattice

We propose that the inhomogeneous patterns seen by STM in some underdoped superconducting cuprates could be related to a bond-order-wave instability of the staggered flux state, one of the most studied "normal" state proposed to compete with the d-wave RVB superconductor. A checkerboard pattern is obtained by a Gutzwiller renormalized mean-field theory of the t-J model for doping around 1/8. It is found that the charge modulation is always an order of magnitude smaller than the bond-order modulations. This is confirmed by an exact optimization of the wavefunction by a variational Monte Carlo scheme. The numerical estimates of the order parameters are however found to be strongly reduced w.r.t their mean-field values

Fractional vortices on grain boundaries --- the case for broken time reversal symmetry in high temperature superconductors

We discuss the problem of broken time reversal symmetry near grain boundaries in a d-wave superconductor based on a Ginzburg-Landau theory. It is shown that such a state can lead to fractional vortices on the grain boundary. Both analytical and numerical results show the structure of this type of state.Comment: 9 pages, RevTeX, 5 postscript figures include

Superconductivity without Local Inversion Symmetry; Multi-layer Systems

While multi-layer systems can possess global inversion centers, they can have regions with locally broken inversion symmetry. This can modify the superconducting properties of such a system. Here we analyze two dimensional multi-layer systems yielding spatially modulated antisymmetric spin-orbit coupling (ASOC) and discuss superconductivity with mixed parity order parameters. In particular, the influence of ASOC on the spin susceptibility is investigated at zero temperature. For weak inter-layer coupling we find an enhanced spin susceptibility induced by ASOC, which hints the potential importance of this aspect for superconducting phase in specially structured superlattices.Comment: 4 pages, 2 figures, proceedings of the 26th International Conference on Low Temperature Physics (LT26

Vínculos de formación y transmisión del conocimiento en la botánica del siglo XVIII : un análisis de redes sociales

En esta contribución se desarrolla un enfoque de redes sociales sobre la formación de los botánicos europeos en el siglo XVIII. En un período en el que el estudio de las plantas se estaba convirtiendo en un campo autónomo de investigación, la práctica de la botánica y otras ciencias relacionadas movilizó a un grupo muy diverso de actores. Para muchos de ellos, la iniciación en la ciencia de las plantas fue parte de sus estudios de medicina. Otros fueron formados como colaboradores de un erudito destacado en el contexto de un jardín real, a veces también en las facultades de filosofía. Otros fueron autodidactas. Con los datos biográficos disponibles hemos realizado un censo sistemático de los maestros y discípulos de un conjunto de 928 botánicos occidentales activos entre 1700 y 1830. De este modo hemos identificado tres subgrupos, cada uno de ellos con distintas características y lógicas de desarrollo. Las características específicas de estos subgrupos se analizan desde una perspectiva histórica, con especial atención a los diversos contextos institucionales que los produjeron. El análisis de los datos muestra la creciente autonomía de la botánica respecto a la formación médica, así como el carácter cada vez más nacional de las escuelas dominantes, al menos en Francia.This contribution develops a social network approach to the training of European botanists in the 18th century. In a period when the study of plants increasingly became an autonomous field of research, the practice of botany and related sciences mobilized a very diverse group of actors. For many of them, initiation to the science of plants was part of their medical studies. Others were trained as collaborators of an outstanding scholar in the context of a royal garden or elsewhere, sometimes also in philosophical faculties. Still others were self-taught. To the extent that biographical data were available, we made a systematic census of the masters and disciples of a set of 928 Western botanists active between 1700 and 1830. Three subsets were thus identified, each of them showing distinct characteristics and logics of development. The specific features of these subsets are discussed in a historical perspective, with a particular attention to the various institutional contexts which produced them. The data analysis basically shows the growing autonomy of botany with regard to medical training, as well as the increasingly national character of the dominant schools, at least in France