Positron deformation potential and the temperature dependence of the electron and positron work functions.

Abstract

The sum of the electron and positron work functions, ${\ensuremath{\varphi}}_{0}$, has been measured for a clean Al(100) surface. As a function of temperature, ${\ensuremath{\varphi}}_{0}$ is found to be proportional to the thermal expansion of the lattice. Using the known thermal expansion coefficient of Al we obtain a value for the positron deformation potential, ${\ensuremath{\varepsilon}}_{d}$=-11.7\ifmmode\pm\else\textpm\fi{}0.5 eV, in poor agreement with theoretical calculations but consistent with the known positron diffusion coefficient.