Interface dependence of the Josephson-current fluctuations in short SNS junctions

We discuss the dependence of the Josephson current correlations in mesoscopic superconductor/normal-conductor/superconductor (SNS) devices on the transparency of the superconductor/normal-conductor (SN) interfaces. Focusing on short junctions we apply the supersymmetry method to construct an effective field theory for mesoscopic SNS devices which is evaluated in the limit of highly and weakly transparent interfaces. We show that the two-point Josephson-current correlator differs by an universal factor 2 in these two cases.Comment: 5 pages, 1figure, version accepted by PR

Measurement of Rashba and Dresselhaus spin-orbit magnetic fields

Spin-orbit coupling is a manifestation of special relativity. In the reference frame of a moving electron, electric fields transform into magnetic fields, which interact with the electron spin and lift the degeneracy of spin-up and spin-down states. In solid-state systems, the resulting spin-orbit fields are referred to as Dresselhaus or Rashba fields, depending on whether the electric fields originate from bulk or structure inversion asymmetry, respectively. Yet, it remains a challenge to determine the absolute value of both contributions in a single sample. Here we show that both fields can be measured by optically monitoring the angular dependence of the electrons' spin precession on their direction of movement with respect to the crystal lattice. Furthermore, we demonstrate spin resonance induced by the spin-orbit fields. We apply our method to GaAs/InGaAs quantum-well electrons, but it can be used universally to characterise spin-orbit interactions in semiconductors, facilitating the design of spintronic devices

Polarisation Patterns and Vectorial Defects in Type II Optical Parametric Oscillators

Previous studies of lasers and nonlinear resonators have revealed that the polarisation degree of freedom allows for the formation of polarisation patterns and novel localized structures, such as vectorial defects. Type II optical parametric oscillators are characterised by the fact that the down-converted beams are emitted in orthogonal polarisations. In this paper we show the results of the study of pattern and defect formation and dynamics in a Type II degenerate optical parametric oscillator for which the pump field is not resonated in the cavity. We find that traveling waves are the predominant solutions and that the defects are vectorial dislocations which appear at the boundaries of the regions where traveling waves of different phase or wave-vector orientation are formed. A dislocation is defined by two topological charges, one associated with the phase and another with the wave-vector orientation. We also show how to stabilize a single defect in a realistic experimental situation. The effects of phase mismatch of nonlinear interaction are finally considered.Comment: 38 pages, including 15 figures, LATeX. Related material, including movies, can be obtained from http://www.imedea.uib.es/Nonlinear/research_topics/OPO

Anomalous Hall effect in paramagnetic two dimensional systems

We investigate the possibility of observing the anomalous Hall effect (AHE) in two dimensional paramagnetic systems. We apply the semiclassical equations of motion to carriers in the conduction and valence bands of wurtzite and zincblende quantum wells in the exchange field generated by magnetic impurities and we calculate the anomalous Hall conductivity based on the Berry phase corrections to the carrier velocity. We show that under certain circumstances this conductivity approaches one half of the conductance quantum. We consider the effect of an external magnetic field and show that for a small enough field the theory is unaltered.Comment: 9 pages, 10 figures, 2 table

Lateral Spin Injection in Germanium Nanowires

Electrical injection of spin-polarized electrons into a semiconductor, large spin diffusion length, and an integration friendly platform are desirable ingredients for spin-based devices. Here we demonstrate lateral spin injection and detection in germanium nanowires, by using ferromagnetic metal contacts and tunnel barriers for contact resistance engineering. Using data measured from over 80 samples, we map out the contact resistance window for which lateral spin transport is observed, manifestly showing the conductivity matching required for spin injection. Our analysis, based on the spin diffusion theory, indicates that the spin diffusion length is larger than 100 {\mu}m in germanium nanowires at 4.2 K

Properties of feedback solitons in a single-mirror experiment

We report on the observation of localized states (LSs) in a single-mirror feedback system using sodium vapor as the nonlinear medium. By combining experimental results with simulations based on a microscopic model and with results of a linear stability analysis of the homogeneous state, we discuss the properties of the LSs, the mechanism of their formation, their domain of existence in parameter space, their interaction with the amplitude and phase gradient in the Gaussian beam of the driving laser, and the formation of 'molecules' and 'clusters' of LSs. We elucidate the dominant role of diffraction in the interaction of the LSs and discuss relations between the clusters of LSs and extended patterns

Haalbaarheidsstudie 2: Recidivemeting forensische zorg. Nader onderzoek naar de ontwikkeling van een recidivemonitor voor de sector forensische zorg

Centraal in deze tweede haalbaarheidsstudie staat de vraag in hoeverre door koppeling van reeds bestaande informatievoorzieningen aan de Justitiële Documentatie uit de OBJD, een betrouwbaar beeld kan worden gegeven van de strafrechtelijke recidive van justitiabelen die vóór 2011 uit één van deze vijf Forensische Zorg-titels zijn uitgestroomd. In de beschrijving van de resultaten wordt onderscheid gemaakt tussen titels die betrekking hebben op forensische zorg tijdens detentie (overbrenging vanuit het gevangeniswezen naar een psychiatrisch ziekenhuis of de hulpverlening) en forensische zorg in het kader van voorwaarden bij een sanctie (voorwaardelijke veroordeling, sepot met voorwaarden en voorwaardelijke invrijheidstelling met bijzondere voorwaarden). Eerste haalbaarheidsstudie (zie link bij: Meer informatie