Exploring the phase diagram of the two-impurity Kondo problem

A system of two exchange-coupled Kondo impurities in a magnetic field gives rise to a rich phase space hosting a multitude of correlated phenomena. Magnetic atoms on surfaces probed through scanning tunnelling microscopy provide an excellent platform to investigate coupled impurities, but typical high Kondo temperatures prevent field-dependent studies from being performed, rendering large parts of the phase space inaccessible. We present an integral study of pairs of Co atoms on insulating Cu2N/Cu(100), which each have a Kondo temperature of only 2.6 K. In order to cover the different regions of the phase space, the pairs are designed to have interaction strengths similar to the Kondo temperature. By applying a sufficiently strong magnetic field, we are able to access a new phase in which the two coupled impurities are simultaneously screened. Comparison of differential conductance spectra taken on the atoms to simulated curves, calculated using a third order transport model, allows us to independently determine the degree of Kondo screening in each phase.Comment: paper: 14 pages, 4 figures; supplementary: 3 pages, 1 figure, 1 tabl

Understanding and managing a complex estuary: the process towards more congruence between the physical system characteristics and the management system of the Westerschelde (Netherlands)

International audienceIn this article, we expand on the relationship between the social processes of policymaking, management and research in the context of the Westerschelde estuary. This complex estuary system, located in Belgium and the Netherlands, has its own morphological and ecological characteristics and dynamics, and has three core functions: economically, it makes the port of Antwerp accessible; ecologically, it generates habitats for certain unique species; and in terms of safety, it prevents the hinterland from being flooded. We analyze how the social processes of policymaking, management and analysis have focused on these three aspects, and how they have affected the estuary. We proceed to develop a framework for evaluating the social system of policy-making, management and research. This framework focuses on the social system's adaptive capabilities (how it evolved in a non-linear fashion), integrative capacity (how the system's interconnectivity was taken into account), and participative competencies (how the different interests and insights regarding the estuary were absorbed). This framework was then applied to twenty years of policymaking about, management of, and research on the Westerschelde estuary. We conclude that, because of policy learning effects, policy/management and research take the estuary's self-organizing capacities into account much more than they did in the past. However, the self-referential behaviour of policymakers, managers and researchers makes it possible that an anthropocentric and technocratic approach towards managing the estuary, indicating a disconnection between the social and physical systems, could return

The Dynamics of Sedimentary Systems and the Whimsicality of Policy Processes

Background, Aims, and Scope. Sediment management in coastal zones is taking place in high complex environments. Present management options do not have a sophisticated way of dealing with the actual complexity of the physical and the social systems and with the unpredictability that is inherent with these systems. Therefore, a new approach in both policy making and sediment management is needed that takes this complexity into account. The aim of this article is to explore the dynamics in social and natural systems and to draw the contours of this new approach for policy processes and sediment management that fits to the dynamics of the systems. Results and Discussion. The case studies show that chance events can occur in the biophysical and in the social system. In the three cases, players or actors in the decision process are left with the choice to adapt themselves to the occurring chance events or to refrain from any adaptive behaviour. Chance events can open up new possibilities by activating (new) actors and by coupling to new issues. If the situation is too locked-in (i.e. a stalemate) and is intentional on behalf of the actors, than the chance event will have no effect. T

Large angle magnetization dynamics measured by time-resolved ferromagnetic resonance

A time-resolved ferromagnetic resonance technique was used to investigate the magnetization dynamics of a 10 nm thin Permalloy film. The experiment consisted of a sequence of magnetic field pulses at a repetition rate equal to the magnetic systems resonance frequency. We compared data obtained by this technique with conventional pulsed inductive microwave magnetometry. The results for damping and frequency response obtained by these two different methods coincide in the limit of a small angle excitation. However, when applying large amplitude field pulses, the magnetization had a non-linear response. We speculate that one possible cause of the nonlinearity is related to self-amplification of incoherence, known as the Suhl instabilities.Comment: 23 pages, 8 figures, submitted to PR

Case-based complexity: within-case time variation and temporal casing

We observe that time is central to most social dynamics and yet remains poorly understood. The complexity sciences have contributed a wide range of concepts and tools to investigate and recast time in social systems. However, the dominant focus on quantitative models and quantification of data in the complexity sciences also prohibits a deeper understanding of time. As such, there is a need to fuse alternative notions of time with how it is commonly understood and measured in the complexity sciences. To this end, we juxtapose diverse notions of time from the social sciences and comment upon how this contrasts with notions in the complexity sciences. We will demonstrate how (qualitative) temporal casing can more appropriately capture social and causal complexity through within-case time variation. We use examples from research into megaprojects to demonstrate how temporal casing plays out in empirical analysis