Tuning the dispersion of 4f bands in the heavy-fermion material YbRh2Si2

Localized Yb 4f and itinerant Rh 4d states are subject to substantial hybridization effects in the heavy-fermion material YbRh₂Si₂. The proximity to the Fermi level and the high anisotropy in k space naturally raise questions regarding the role of these hybridization effects for the observed, unusual physical properties. Using angle-resolved photoemission spectroscopy (ARPES) we found that the non-dispersive behavior of the localized Yb f states is broken around the Γ point due to interaction with approaching Rh 4d bands. The intriguing point here is that the hybridization strength turns out to be systematically tunable by electron doping of the material. Gradual deposition of silver atoms onto the atomically clean, silicon terminated surface of YbRh₂Si₂ leads to transfer of Ag 5s charge into the Rh 4d bands. This substantially changes the energy overlap, and thus the hybridization strength, between the interacting Yb 4f and Rh 4d bands in the surface and subsurface region. The shown possibility to control the variation of the f-d hybridization at the surface of heavy-fermion materials may also be helpful for other ARPES studies on the diverse phenomena in electron-correlated materials.     

A particle–particle hybrid method for kinetic and continuum equations

We present a coupling procedure for two different types of particle methods for the Boltzmann and the Navier–Stokes equations. A variant of the DSMC method is applied to simulate the Boltzmann equation, whereas a meshfree Lagrangian particle method, similar to the SPH method, is used for simulations of the Navier–Stokes equations. An automatic domain decomposition approach is used with the help of a continuum breakdown criterion. We apply adaptive spatial and time meshes. The classical Sod’s 1D shock tube problem is solved for a large range of Knudsen numbers. Results from Boltzmann, Navier–Stokes and hybrid solvers are compared. The CPU time for the hybrid solver is 3–4 times faster than for the Boltzmann solver.     

Controller Design for a Test Bench for Seat Belt Systems

In the product development of vehicle seat belt systems there is a strong need for the possibility of an isolated component testing that is comparable to real world car crashes. A test bench concept that is able to fulfill this requirement is presented. This test bench mainly consists of a highly dynamic actuator system for which a control scheme is presented. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analytical solution of the PNP equations at AC applied voltage

A symmetric binary polymer electrolyte subjected to an AC voltage is considered. The analytical solution of the Poisson–Nernst–Planck equations (PNP) is found and analyzed for small applied voltages. Three distinct time regimes offering different behavior can be discriminated. The experimentally realized stationary behavior is discussed in detail. An expression for the external current is derived. Based on the theoretical result a simple method is suggested of measuring the ion mobility and their concentration separately.     

Probing the unconventional superconducting state of LiFeAs by quasiparticle interference

A crucial step in revealing the nature of unconventional superconductivity is to investigate the symmetry of the superconducting order parameter. Scanning tunneling spectroscopy has proven a powerful technique to probe this symmetry by measuring the quasiparticle interference (QPI) which sensitively depends on the superconducting pairing mechanism. A particularly well-suited material to apply this technique is the stoichiometric superconductor LiFeAs as it features clean, charge neutral cleaved surfaces without surface states and a relatively high T(c)～18 K. Our data reveal that in LiFeAs the quasiparticle scattering is governed by a van Hove singularity at the center of the Brillouin zone which is in stark contrast to other pnictide superconductors where nesting is crucial for both scattering and s(±) superconductivity. Indeed, within a minimal model and using the most elementary order parameters, calculations of the QPI suggest a dominating role of the holelike bands for the quasiparticle scattering. Our theoretical findings do not support the elementary singlet pairing symmetries s(++), s(±), and d wave. This brings to mind that the superconducting pairing mechanism in LiFeAs is based on an unusual pairing symmetry such as an elementary p wave (which provides optimal agreement between the experimental data and QPI simulations) or a more complex order parameter (e.g., s+id wave symmetry).     

Modular deposition chamber for in situ X‐ray experiments during RF and DC magnetron sputtering

A new sputtering system for in situ X‐ray experiments during DC and RF magnetron sputtering is described. The outstanding features of the system are the modular design of the vacuum chamber, the adjustable deposition angle, the option for plasma diagnostics, and the UHV sample transfer in order to access complementary surface analysis methods. First in situ diffraction and reflectivity measurements during RF and DC deposition of vanadium carbide demonstrate the performance of the set‐up.     

Dissecting Fragment-Based Lead Discovery at the von Hippel-Lindau Protein:Hypoxia Inducible Factor 1α Protein-Protein Interface

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Highlights? Inhibitors of pVHL:HIF-1α interaction are ligand-efficient and retain binding mode ? Ro3-compliant fragments of these inhibitors are not hits in biophysical screens ? Successful hit fragments break the Ro3 and target at least two subsites at the PPI ? Integration of GE and GLE analyses provide methodology to probe hot spots at a PPI     

An inorganic propellane with central B-B bond

9,10-Dihydroanthracene-9,10-diyl-bridged B(2)(NMe(2))(2) readily adds [H(2)NMe(2)](+), HCl and F(3)CCOOH across its partial B=N double bond(s), thereby forming mono- or diadducts; treatment with 1-iso-propyl-2-mercaptoimidazole leads to a triply B-B-bridged propellane-like structure.