[en] Recently a non-vanishing supercurrent has been observed in a Josephson junction that contains an extended region of half-metallic CrO₂ between two singlet superconducting electrodes. A theory to explain this phenomenon has been established in Refs. [2,3] that is formulated in terms of spin-active interface scattering matrices. Spin mixing and breaking of spin-rotation symmetry around the magnetization axis of the half metal are necessary ingredients for creation of equal spin triplet pairing amplitudes that can penetrate the half metal over a long range. Here, we present a microscopic model for a scattering matrix that exhibits such characteristics. We show that disorder of local magnetic moments at the interface between a superconductor and a ferromagnet with biaxial anisotropy in the interface region leads to the observed current conversion between singlet and equal spin triplet supercurrents. We discuss our results by comparing with the experimental findings of biaxial anisotropy and triplet supercurrents in the half metal CrO₂. (orig.)

[en] Recently a new method to set the scale in lattice gauge theories, based on the gradient flow generated by the Wilson action, has been proposed, and the systematic errors of the new scales t₀ and w₀ have been investigated by various groups. The Wilson flow provides also an interesting alternative smoothing procedure in particular useful for the measurement of the topological charge as a pure gluonic observable. We show the viability of this method for N=1 supersymmetric Yang-Mills theory by analysing the configurations produced by the DESY-Muenster collaboration. For increasing flow time the topological charge quickly approaches near-integer values. The topological susceptibility has been measured for different fermion masses and its value is observed to approach zero in the chiral limit. Finally, the relation between the scale defined by the Wilson flow and the topological charge has been investigated, demonstrating a correlation between these two quantities.

[en] We present the current results of our simulations of N=1 supersymmetric Yang-Mills theory on a lattice. The masses of the gluino-glue particle, the a-η', the a-f₀ meson, and the scalar glueball are obtained at finer lattice spacing than before, and extrapolations towards vanishing gluino mass are made. The calculations employ different levels of stout smearing. The statistical accuracy as well as the control of finite size effects and lattice artefacts are better than in previous investigations. Taking the statistical and systematic uncertainties into account, the extrapolations towards vanishing gluino mass of the masses of the fermionic and bosonic states in our present calculations are consistent with the formation of degenerate supermultiplets.

[en] We consider a three-dimensional effective theory of Polyakov lines derived previously from lattice Yang-Mills theory and QCD by means of a resummed strong coupling expansion. The effective theory is useful for investigations of the phase structure, with a sign problem mild enough to allow simulations also at finite density. In this work we present a numerical method to determine improved values for the effective couplings directly from correlators of 4d Yang-Mills theory. For values of the gauge coupling up to the vicinity of the phase transition, the dominant short range effective coupling are well described by their corresponding strong coupling series. We provide numerical results also for the longer range interactions, Polyakov lines in higher representations as well as four-point interactions, and discuss the growing significance of non-local contributions as the lattice gets finer. Within this approach the critical Yang-Mills coupling β_c is reproduced to better than one percent from a one-coupling effective theory on N_τ=4 lattices while up to five couplings are needed on N_τ=8 for the same accuracy.

[en] A simplified setup for coherent anti-Stokes Raman scattering (CARS) microscopy is introduced, which allows for recording CARS images with 30 cm^-1 excitation bandwidth for probing Raman bands between 500 and 900 cm^-1 with minimal requirements for alignment. The experimental arrangement is based on electronic switching between CARS images recorded at different Raman resonances by combining a photonic crystal fiber (PCF) as broadband light source and an acousto-optical programmable dispersive filter (AOPDF) as tunable wavelength filter. Such spatial light modulator enables selection of a narrow-band spectrum to yield high vibrational contrast and hence chemical contrast in the resultant CARS images. Furthermore, an experimental approach to reconstruct spectral information from CARS image contrast is introduced

[en] In many laser spectroscopic techniques, such as fluorescence Raman and resonance Raman spectroscopy the choice of laser excitation wavelength is of central importance. Thus, it is desirable to have a single laser light source where the wavelength can be tuned fast, easily and continuously without the necessity of changing the optical alignment. Here, such a light source is presented combining a broad spectrum with a spatial light modulator as tunable filter. The feasibility of this setup for Raman spectroscopy is demonstrated

[en] In this letter we present an approach to CARS microscopy, which compromises between fast acquisition rates and the amount of chemical information obtained. By using a light modulator as tunable filter in concert with narrowband pump and broadband Stokes pulses, we demonstrate an experimental arrangement, which allows for fast electronic switching between CARS images recorded at different Raman resonances without the need for any optical adjustment

[en] A three-dimensional effective theory of Polyakov loops has recently been derived from Wilson’s Yang-Mills lattice action by means of a strong coupling expansion. It is valid in the confined phase up to the deconfinement phase transition, for which it predicts the correct order and gives quantitative estimates for the critical coupling. In this work we study its predictive power for further observables like correlation functions and the equation of state. We find that the effective theory correctly reproduces qualitative features and symmetries of the full theory as the continuum is approached. Regarding quantitative predictions, we identify two classes of observables by numerical comparison as well as analytic calculations: correlation functions and their associated mass scales cannot be described accurately from a truncated effective theory, due to its inherently non-local nature involving long-range couplings. On the other hand, phase transitions and bulk thermodynamic quantities are accurately reproduced by the leading local part of the effective theory. In particular, the effective theory description is numerically superior when computing the equation of state at low temperatures or the properties of the phase transition

[en] We study and simulate N=2 supersymmetric Wess-Zumino models in one and two dimensions. For any choice of the lattice derivative, the theories can be made manifestly supersymmetric by adding appropriate improvement terms corresponding to discretizations of surface integrals. In one dimension, our simulations show that a model with the Wilson derivative and the Stratonovich prescription for this discretization leads to far better results at finite lattice spacing than other models with Wilson fermions considered in the literature. In particular, we check that fermionic and bosonic masses coincide and the unbroken Ward identities are fulfilled to high accuracy. Equally good results for the effective masses can be obtained in a model with the SLAC derivative (even without improvement terms). In two dimensions we introduce a non-standard Wilson term in such a way that the discretization errors of the kinetic terms are only of order O(a²). Masses extracted from the corresponding manifestly supersymmetric model prove to approach their continuum values much quicker than those from a model containing the standard Wilson term. Again, a comparable enhancement can be achieved in a theory using the SLAC derivative