Combinatorial sputtering in planetary type systems for alloy libraries with perpendicular gradients of layer thickness and composition realised by a timing approach

We present a combinatorial sputtering technique to fabricate alloy thin films with orthogonal gradients of thickness and stoichiometry in a planetary type sputtering system. Using this approach we prepared a library of planar Nb Josephson junctions with a magnetic compound layer made from Si and Fe on one wafer. The independent investigation of thickness and composition changes of the Fe \(_x\) Si \(_{1-x}\) layer allows the identification of transition regions where the phase difference of the superconducting order parameter across the barrier changes from 0 to \(\pi \) . A mapping technique which allows to identify the different coupling regimes depending on material properties might facilitate the fabrication of \(\pi \) junctions with tailored critical current, damping and normal resistance parameters for applications.     

Admissible sequences and the preprojective component of a quiver

This paper concerns indecomposable preprojective modules over the path algebra of a finite connected quiver without oriented cycles. For each such module, an explicit formula in terms of the geometry of the quiver gives a unique, up to a certain equivalence, shortest (+)-admissible sequence such that the corresponding composition of reflection functors annihilates the module. An efficient way to compute the module is to recover it from its shortest (+)-admissible sequence. The set of equivalence classes of the above sequences has a natural structure of a partially ordered set. For a large class of quivers, the Hasse diagram of the partially ordered set is isomorphic to the preprojective component of the Auslander-Reiten quiver. The techniques of (+)-admissible sequences yield a new result about slices in the preprojective component.     

Metallic subwavelength structures for a broadband infrared absorption control

We present a method to control the absorption of a resonator by using a subwavelength structure consisting of thin metallic plates that behaves as a metamaterial film. We demonstrate the ability to tailor the conductivity of such a metallic subwavelength structure to achieve a resonator with the desired impedance matching for the mid-infrared range. This approach provides for broadband, as well as broad-angle, enhanced absorption. Theoretical analyses, as well as experimental results of the optical properties of a metallic NiCr structure at 8-12 microm spectral range are introduced.     

Low barrier methyl rotation in 3-pentyn-1-ol as observed by microwave spectroscopy

ABSTRACT

The rotational spectrum of 3-pentyn-1-ol, CH₃?C≡C?CH₂CH₂OH, was measured using a molecular beam Fourier transform microwave spectrometer operating in the frequency range from 2 to 26.5 GHz. A two-dimensional potential energy surface was calculated at the MP2/6-311++G(d,p) level of theory for a conformational analysis, yielding five conformers. The most stable conformer exhibits C₁ symmetry and was assigned in the spectrum by comparison with the results from quantum chemical calculations. The barrier to internal rotation of the propynyl methyl group CH₃?C≡C? was found to be only 9.4552(94) cm^?1. Molecular parameters and internal rotation parameters could be accurately determined using the program xiam and belgi-C₁. The internal rotation barrier was compared with those of other molecules containing a propynyl methyl group.     

Global modeling of the lower three polyads of PH3: Preliminary results

In order to model the high-resolution infrared spectrum of the phosphine molecule in the 3 μm region, a global approach involving the lower three polyads of the molecule (Dyad, Pentad and Octad) as been applied using an effective hamiltonian in the form of irreducible tensors. This model allowed to describe all the 15 vibrational states involved and to consider explicitly all relevant ro-vibrational interactions that cannot be accounted for by conventional perturbation approaches. 2245 levels (up to J = 14) observed through transitions arising from 34 cold and hot bands including all available existing data as well as new experimental data have been fitted simultaneously using a unique set of effective hamiltonian parameters. The rms achieved is 0.63 × 10⁻³ cm⁻¹ for 450 Dyad levels, 1.5 × 10⁻³ cm⁻¹ for 1058 Pentad levels (from 3585 transitions) and 4.3 × 10⁻³ cm⁻¹ for 737 Octad levels (from 2243 transitions). This work represents the first theoretical modeling of the 3 μm region. It also improves the modeling of the region around 4.5 μm by dividing the rms reported by previous works by a factor 6. A preliminary intensity analysis based on consistent sets of effective dipole moment operators for cold and hot bands has been simultaneously undertaken for direct comparison between observed and modeled absorption from 700 to 3500 cm⁻¹.     

0-pi Josephson tunnel junctions with ferromagnetic barrier

We fabricated high quality Nb/Al2O3/Ni(0.6)Cu(0.4)/Nb superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions. Using a ferromagnetic layer with a steplike thickness, we obtain a 0-pi junction, with equal lengths and critical currents of 0 and pi parts. The ground state of our 330 microm (1.3lambda(J)) long junction corresponds to a spontaneous vortex of supercurrent pinned at the 0-pi step and carrying approximately 6.7% of the magnetic flux quantum Phi(0). The dependence of the critical current on the applied magnetic field shows a clear minimum in the vicinity of zero field.     

Multiple Quantum Coherences Hyperpolarized at Ultra-Low Fields

The development of hyperpolarization technologies enabled several yet exotic NMR applications at low and ultra-low fields (ULF), where without hyperpolarization even the detection of a signal from analytes is a challenge. Herein, we present a method for the simultaneous excitation and observation of homo- and heteronuclear multiple quantum coherences (from zero up to the third-order), which give an additional degree of freedom for ULF NMR experiments, where the chemical shift variation is negligible. The approach is based on heteronuclear correlated spectroscopy (COSY); its combination with a phase-cycling scheme allows the selective observation of multiple quantum coherences of different orders. The nonequilibrium spin state and multiple spin orders are generated by signal amplification by reversible exchange (SABRE) and detected at ULF with a superconducting quantum interference device (SQUID)-based NMR system.