POSITRON-ANNIHILATION FROM NEARLY LOCALIZED FERMI LIQUIDS - A PROBE OF PAIRING

Based on a theory of position annihilation from systems with strongly correlated electrons, it is predicted that positron-annihilation spectroscopy (PAS) can be an extremely useful probe of pairing and superconductivity in such systems. Specifically, it is shown that if the nearly localized electrons form pairs which are small, then the annihilation characteristics are changes significantly from those in the unpaired state, and the changes reflect both the amplitude and the symmetry of the order parameter. This has obvious consequences for the high-temperature superconductors which have small coherence lengths and where, it has been argued, the Hubbard-model description may be appropriate.