Ruben Weht

Half-metallic ferrimagnetism in Mn 2 VAl

We show that

Mechanism for bipolar resistive switching in transition metal oxides

{\mathrm{Mn}}_{2}\mathrm{VAl}

SUPERCONDUCTIVITY IN FERROMAGNETIC RUSR2GDCU2O8

is a compound for which the generalized gradient approximation (GGA) to the exchange-correlation functional in density functional theory makes a qualitative change in predicted behavior compared to the usual local density approximation. Application of GGA leads to prediction of

Excitonic correlations in the intermetallic Fe 2 VAl

{\mathrm{Mn}}_{2}\mathrm{VAl}

Magnetism in atomic-size palladium contacts and nanowires

being a half-metallic ferrimagnet, with the minority channel being the conducting one. The electronic and magnetic structure is analyzed and contrasted with the isostructural enhanced semimetal

New superhard phases for three-dimensional C60-based fullerites

{\mathrm{Fe}}_{2}\mathrm{VAl}.

Semimetallic antiferromagnetism in the half-Heusler compound CuMnSb

We introduce a model that accounts for the bipolar resistive switching phenomenon observed in transition-metal oxides. It qualitatively describes the electric-field-enhanced migration of oxygen vacancies at the nanoscale. The numerical study of the model predicts that strong electric fields develop in the highly resistive dielectric-electrode interfaces leading to spatially inhomogeneous oxygen vacancies distribution and a concomitant resistive switching effect. The theoretical results qualitatively reproduce nontrivial resistance hysteresis experiments that we also report providing key validation to our model.

Electronic fine structure in the electron-hole plasma in SrB6

Relying on the inhomogeneous (layered) crystal, electronic, and magnetic structure, we show how superconductivity can coexist with the ferromagnetic phase of RuSr2GdCu2O8 as observed by Tallon and coworkers. Since the Cu d_{x^2-y^2} orbitals couple only to apical O p_x, p_y orbitals (and only weakly), which also couple only weakly to the magnetic Ru t_{2g} orbitals, there is sufficiently weak exchange splitting, especially of the symmetric CuO2 bilayer Fermi surface, to allow singlet pairing. The exchange splitting is calculated to be large enough that the superconducting order parameter may be of the Fulde-Ferrell-Larkin-Ovchinnikov type. We also note that \pi-phase formation is preferred by the magnetic characteristics of RuSr2GdCu2O8.

First-order insulator-to-metal Mott transition in the paramagnetic 3D system GaTa4Se8.

The intermetallic compound