SQUEEZED EXCITED-STATES IN EXCITON-PHONON SYSTEMS

In earlier work unusual excited exciton-phonon states have been found for prototype exciton-phonon Hamiltonians (dimer, trimer). These states have been calculated numerically by diagonalizing the respective Fulton-Gouterman equations. Their physical character is such that the motion of the effective exciton becomes free whereas in the vibrational subspace the dynamics is governed by an effective stiffening of the nearest-neighbor interaction. In the present work it is shown analytically by means of a Fröhlich-type transformation, how the stiffening in the phonon dynamics is generated, such that the phononic part for these nonconventional exciton-phonon states is well described by squeezed oscillatory functional forms. © 1995 The American Physical Society.