We calculate the tunneling rate of a heavy particle in a metal, which can hop between two sites at ±a with a frequency rate Δ/(2ħ) and can interact with the conduction electrons with the screened potential G. The tunneling rate presents an asymmetric peak, centered at the reduced energy ${\mathrm{\Delta }}^{\mathrm{*}}$, that decreases with increasing G. The integrated tunneling rate has a finite value for the phase shift at the Fermi level ${\mathrm{\delta }}_0$=π/2. Our results point to no localization of the heavy particle in this model.

• Received 30 August 1993

DOI:https://doi.org/10.1103/PhysRevB.49.2152