526 research outputs found
Exchange interaction and Fano resonances in diatomic molecular systems
We propose a mechanism to use scanning tunneling microscopy (STM) for direct
measurements of the two-electron singlet-triplet exchange splitting in
diatomic molecular systems, unsing the coupling between the molecule and the
substrate electrons. The different pathways for electrons lead to interference
effects and generate kinks in the differential conductance at the energies for
the singlet and triplet states. These features are related to Fano resonance
due to the branched electron wave functions. The ratio between the tunneling
amplitudes through the two atoms can be modulated by spatial movements of the
tip along the surface.Comment: 4 pages, 2 figures, submitted - Changes in Fig. 1 (panel c) added),
and minor modification in the main text - new version, as publishe
Impurities and Conductivity in a D-wave Superconductor
Impurity scattering in the unitary limit produces low energy quasiparticles
with anisotropic spectrum in a two-dimensional -wave superconductor. We
describe a new {\em quasi-one-dimensional } limit of the quasiparticle
scattering, which might occur in a superconductor with short coherence length
and with {\em finite} impurity potential range. The dc conductivity in a
-wave superconductor is predicted to be proportional to the normal state
scattering rate and is impurity-{\em dependent}. We show that {\em
quasi-one-dimensional } regime might occur in high- superconductors with
Zn impurities at low temp\ eratures ~KComment: 6 pages , Revtex 3, Los Alamos Preprint LA-UR-94-9
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