Effective Mass of the Positron in Sodium

Abstract

The band effective mass of the positron in sodium is computed by the standard method of Wigner, Seitz, and Bardeen. The result is $m^{*}=1.06m$, where $m$ is the free-particle mass. Combining it with the results of the many-body calculations of the effective mass of a positron interacting with a Fermi sea of electrons, one can conclude that the theoretical value is much smaller than the experimentally observed effective mass.