Spin Hamiltonian of Hyperkagome Na4Ir3O8

We derive the spin Hamiltonian for the quantum spin liquid Na4Ir3O8, and then estimate the direct and superexchange contributions between near neighbor iridium ions using a tight binding parametrization of the electronic structure. We find a magnitude of the exchange interaction comparable to experiment for a reasonable value of the on-site Coulomb repulsion. For one of the two tight binding parametrizations we have studied, the direct exchange term, which is isotropic, dominates the total exchange. This provides support for those theories proposed to describe this novel quantum spin liquid that assume an isotropic Heisenberg model.Comment: 9 pages, 4 figure

Electronic Structure of Hyperkagome Na4Ir3O8

We investigate the electronic structure of the frustrated magnet Na4Ir3O8 using density functional theory. Due to strong spin-orbit coupling, the hyperkagome lattice is characterized by a half-filled complex of states, making it a cubic iridium analogue of the high temperature superconducting cuprates. The implications of our results for this unique material are discussed.Comment: expanded discussion with extra figures - 6 pages, 10 figure

Overview of cases before the CJEU on European Consumer Contract Law (2008–2013) – Part II

During the last five years the CJEU had to decide on more than 50 preliminary references in the area of consumer contract law. As a consequence there are far more than 100 decisions available which represent the increasingly concrete basis for a European contract law. Particularly striking is the rising number of questions referred to the CJEU by the new Member States. With regard to quantity, two fields stand out: legal conflicts about financial services of all kinds and about passenger rights. Since the CJEU has developed independent dogmatics for some areas of contract law, it might be necessary to rethink legal categories on the national level.Durant les cinq dernières années, la CJUE a dû répondre à plus de 50 questions préjudicielles dans le domaine du droit des contrats de consommation. En conséquence, il y a bien plus de 100 décisions disponibles qui représentent une base concrète croissante pour un droit européen des contrats. L’accroissement du nombre de questions adressées à la CJUE par les nouveaux Etats membres est particulièrement frappant. Quantitativement, deux domaines se distinguent : les conflits juridiques relatifs aux services financiers de toutes sortes et ceux relatifs auxprétations propres dans quelques domaines du droit des contrats, il pourrait être nécessaire de repenser les catégories juridiques au niveau national.In den letzten fünf Jahren hatte der EuGH mehr als 50 Vorlageverfahren zu entscheiden. Per dato liegen damit weit mehr als 100 Entscheidungen vor, die in immer dichterer Form die Grundlagen für ein europäisches Vertragsrecht konkretisieren. Auffällig ist die steigende Zahl von Vorlagen aus den neuen Mitgliedstaaten. In der Sache dominieren in quantitativer Hinsicht zwei Bereiche: rechtliche Auseinandersetzungen um Finanzdienstleistungen jedweder Art und das Passagier- bzw. Reiserecht. Für Teilbereiche des Vertragsrechts entwickelt der EuGH eine eigenständige Dogmatik, die ein Überdenken nationaler rechtlicher Kategorien notwendig macht

Controlled switching between paramagnetic and diamagnetic Meissner effect in Pb/Co nanocomposites

A hybrid system which consists of a superconducting (SC) Pb film (100 nm thickness) containing $\sim$1 vol% single domain ferromagnetic (FM) Co particles of mean-size $\sim$4.5 nm reveal unusual magnetic properties: (i) a controlled switching between the usual diamagnetic and the unusual paramagnetic Meissner effect in field cooling as well as in zero-field cooling experiments (ii) amplification of the positive magnetization when the sample enters the SC state below T$_c$. These experimental findings can be explained by the formation of spontaneous vortices and the possible alignment of these vortices due to the foregoing alignment of the Co particle FM moments by an external magnetic field.Comment: 5 pages, 3 figure

Choice Architectures in the Digital Economy: Towards a New Understanding of Digital Vulnerability

In the digital economy, consumer vulnerability is not simply a vantage point from which to assess some consumers’ lack of ability to activate their awareness of persuasion. Instead, digital vulnerability describes a universal state of defencelessness and susceptibility to (the exploitation of) power imbalances that are the result of the increasing automation of commerce, datafied consumer–seller relations, and the very architecture of digital marketplaces. Digital vulnerability, we argue, is architectural, relational, and data-driven. Based on our concept of digital vulnerability, we demonstrate how and why using digital technology to render consumers vulnerable is the epitome of an unfair digital commercial practice

Assessing the Cross-Market Generalization Capability of the CLAUDETTE System

We present a study aimed at testing the CLAUDETTE system's ability to generalise the concept of unfairness in consumer contracts across diverse market sectors. The data set includes 142 terms of services grouped in five sub-sets: travel and accommodation, games and entertainment, finance and payments, health and well-being, and the more general others. Preliminary results show that the classifier has satisfying performance on all the sectors

Kondo decoherence: finding the right spin model for iron impurities in gold and silver

We exploit the decoherence of electrons due to magnetic impurities, studied via weak localization, to resolve a longstanding question concerning the classic Kondo systems of Fe impurities in the noble metals gold and silver: which Kondo-type model yields a realistic description of the relevant multiple bands, spin and orbital degrees of freedom? Previous studies suggest a fully screened spin $S$ Kondo model, but the value of $S$ remained ambiguous. We perform density functional theory calculations that suggest $S = 3/2$. We also compare previous and new measurements of both the resistivity and decoherence rate in quasi 1-dimensional wires to numerical renormalization group predictions for $S=1/2,1$ and 3/2, finding excellent agreement for $S=3/2$.Comment: 4 pages, 4 figures, shortened for PR