Abstract
The ground state of the model of a two-state system coupled with phonons is studied by a variational method. Two trial states, the displaced state, and the displaced-squeezed state, for the phonon subsystem are compared, and their dependence on tunneling parameter Δ, phonon frequency ω, and coupling strength g is analyzed. We find that for Δ/ω≪1 the displaced state is more stable for g/ω<1, while the displaced-squeezed state is preferable for g/ω>1.
- Received 17 July 1989
DOI:https://doi.org/10.1103/PhysRevB.40.11326
©1989 American Physical Society
