Gebundene Paare in Fermi-Flüssigkeiten

The effect of a hard core on the energy of bound pair states in fermi-liquids is considered. It turns out that such bound pairs can exist in nuclear matter for the real nuclear forces, but not in the (non superfluid) He³. The importance of this fact for a possible understanding of the superfluidity is discussed briefly.     

Ladungstransport in dünnen Filmen

The electronic charge transport in thin indium films of high purity is investigated (direct current, eddy current and magnetoresistance in a magnetic field perpendicular to the surface) at low temperatures where surface scattering of the electrons becomes important. A method is described which allows the determination of the mean free path (corresponding to a Sommerfeld-model for the conduction electrons) for a single specimen by measuring both the direct current conductivity and the decay time of eddy currents. For a multivalent metal like indium, with a Fermi surface extending over different Brillouin zones, the “mean free path” evaluated in this way can no longer be regarded as the mean value of the electronic free path calculated over the whole Fermi surface. It is shown, that for indium the ?mean free path” evaluated from our size effect investigations will mainly correspond to the electrons of the second zone, and that the electrons of the third zone only neglectingly contribute to the electronic charge transport.     

Zur Kernfusion in Myonmolekülen

Using results of a preceding paper, the wavefunctions of nuclear vibrations in muon molecules have been calculated by numerical integration, especially at small nuclear distances. These functions have then been used to determine reaction rates of nuclear fusion. The effect of nuclear forces on the wavefunction at very small distances has been estimated and taken account of. The numerical results reasonably agree with (pμd) experiments.     

Spin transition in magnesiowüstite in earth's lower mantle

Iron in the major lower mantle (LM) minerals undergoes a high spin (HS) to low spin (LS) transition at relevant pressures (23-135 GPa). Previous failures of standard first principles approaches to describe this phenomenon have hindered its investigation and the clarification of important consequences. Using a rotationally invariant formulation of LDA + U we report a successful study of this transition in low solute concentration magnesiowüstite, (Mg(1-x)Fe(x)(O), (x < 0.2) the second most abundant LM phase. We show that the HS-LS transition goes through an insulating (semiconducting) intermediate mixed spins (MS) state without discontinuous changes in properties, as seen experimentally. We show that the HS state crosses over smoothly to the LS state passing through an insulating MS state where properties change continuously, as seen experimentally.