Searching for a quantum critical point in YbCu5-xAux

Structural, magnetic, transport and thermal properties of YbCu5-xAux alloys with Au concentration between the limit of structural stability of AuBe5 type at x = 0.4 up to x = 0.7 are reported. The outstanding features of this system are: i) the constant and record high values of Cm /T 7J/molK^2 below a characteristic temperature T*, ranging between 150 mK and 350 mK. ii) A power law thermal dependence dependence Cm/T(T>T*)=A/T^q, with q = 1.3 +/- 0.1, and iii) an arising incoherent electronic scattering observed in the resistivity at T < 1K for x < 0.6 despite the fact that Yb magnetic atoms are placed in a lattice. Magnetic frustration, originated in the tetrahedral distribution of Yb atoms, appears as the responsible of the exotic behavior of this system.Comment: 14 pages, 9 figure

YbPd2In : A promising candidate for strong entropy accumulation at very low temperature

We report on synthesis, crystal structure, magnetic, thermodynamic, and transport properties of the compound YbPd2In, crystallizing as a Heusler structure type. A trivalent state of the rare earth was determined by fitting the magnetic susceptibility with a Curie-Weiss law. This compound is characterized by showing very weak magnetic interactions and a negligible Kondo effect. A specific-heat jump was observed at T 48250mK, followed at higher temperature by a power-law decrease of CP(T)/T. The resulting large electronic entropy increase at very low temperature is rapidly shifted to higher temperature by the application of magnetic field. This magnetocaloric effect places YbPd2In as a very good candidate for adiabatic demagnetization cooling processes

The energy gap of intermediate-valent SmB6 studied by point-contact spectroscopy

We have investigated the intermediate valence narrow-gap semiconductor SmB6 at low temperatures using both conventional spear-anvil type point contacts as well as mechanically controllable break junctions. The zero-bias conductance varied between less than 0.01 mikrosiemens and up to 1 mS. The position of the spectral anomalies, which are related to the different activation energies and band gaps of SmB6, did not depend on the the contact size. Two different regimes of charge transport could be distinguished: Contacts with large zero - bias conductance are in the diffusive Maxwell regime. They had spectra with only small non-linearities. Contacts with small zero - bias conductance are in the tunnelling regime. They had larger anomalies, but still indicating a finite 45 % residual quasiparticle density of states at the Fermi level at low temperatures of T = 0.1 K. The density of states derived from the tunelling spectra can be decomposed into two energy-dependent parts with Eg = 21 meV and Ed = 4.5 meV wide gaps, respectively.Comment: 9 pages incl. 13 figure

Constraints to Economic Development and Growth in the Middle East and North Africa

When comparing the speed and extent of economic development in different geographic regions of the world over the past 20 years, the under-average performance of Arab countries in general and Arab Mediterranean countries in particular is striking. This is despite an overall favorable geo-strategic situation at the crossroads of three continents, with excellent connections to sea and waterways and in direct proximity to the European Union, one of the world’s economic hubs. It is also despite the minor importance of negative factors such as a high-burden diseases or high levels of ethnic fractionalization. In this paper, I focus on identifying the most important constraints on Arab Mediterranean economic development. I use state-of-the-art econometric tools to quantify constraints that have been identified through economic theory and studies of the political economy characteristics of the region. The empirical results offer support for the central hypothesis that limited technological capacities and political economy structures are the primary constraints on economic development. With a view to international structural adjustment efforts, my findings imply that the limited success of the Euro-Mediterranean policy to stimulate the economic development of the Arab Mediterranean countries might be because structural adjustment efforts do not tackle—or at least do not sufficiently tackle— these constraints.Vergleicht man Geschwindigkeit und Umfang der wirtschaftlichen Entwicklung der verschiedenen Weltregionen in den vergangenen zwanzig Jahren, so fällt insbesondere das unterdurchschnittliche Abschneiden der arabischen Länder im Allgemeinen und der arabischen Mittlemeerländer im Besonderen ins Auge, und dies trotz einer insgesamt vorteilhaften geographischen Lage im Schnittpunkt dreier Kontinente mit exzellenten Anschlussmöglichkeiten an See- und Wasserwege, trotz der direkten Nachbarschaft zum Weltwirtschaftsdrehkreuz Europäische Union und trotz der relativ geringen Bedeutung wichtiger entwicklungshemmender Faktoren, beispielsweise ethnische Zersplitterung oder massive Ausbreitung von Krankheiten wie AIDS oder Malaria. In diesem Aufsatz wird versucht, von den unterschiedlichen Hemmfaktoren wirtschaftlicher Entwicklung, die in der wirtschaftstheoretischen Literatur und/oder in MENARegionalstudien diskutiert werden, diejenigen herauszuarbeiten, die wirtschaftliche Entwicklung am stärksten behindern oder möglicherweise stärker als andere. Dabei benutze ich modernste ökonometrische Verfahren, um den Einfluss der verschiedenen erklärenden Variablen zu quantifizieren. Die Ergebnisse stützen die Eingangshypothese, dass insbesondere mangelnde technologische Kapazitäten und Fähigkeiten sowie regionalspezifische politökonomische Strukturen die wirtschaftliche Entwicklung in den arabischen Mittelmeerländern behindern