First excited state calculation using different phonon bases for the two-site Holstein model

摘要

The single-electron energy and static charge-lattice deformation correlationshave been calculated for the first excited state of a two-site Holstein modelwithin perturbative expansions using different standard phonon bases obtainedthrough Lang-Firsov (LF) transformation, LF with squeezed phonon states,modified LF, modified LF transformation with squeezed phonon states, and alsowithin weak-coupling perturbation approach. Comparisons of the convergence ofthe perturbative expansions for different phonon bases reveal that modified LFapproach works much better than other approaches for major range of thecoupling strength.