Small polaron binding energy

The time needed to dress an injected free carrier with phonons (i.e., to form a polaron) is on the order of a phonon period < 1 ps. Therefore, if polaron formation occurs at all, it will be instantaneous compared to a transit time the moving charges begin their transit as polarons. In fact, if the polaron binding energy relative to the free carrier state is small [272], there is a sizable probability that the corresponding nuclear geometric... 

In Ae small polaron picture, on the other hand, the electron-phonon interaction, compounded by the localization effects introduced by the disorder, leads to the formation of small polarons. The polaron binding energy is then the largest energy in the problem, and charge transport involves multiphonon-assisted hopping of small polarons (Emin, 1984). 

A small polaron is normally bound to a donor (or acceptor) on a lattice site at a distance R with the binding energy... 

If the concept of spin polarons as described here is correct, the most important theoretical problem at the present time is to describe the way in which they are bound together to form bosons, of dimensions about 20 A and with binding energy of the order of the Neel temperature. Any binding mechanism will certainly distort the surrounding lattice, so the cohesion may well involve dielectric or dynamic Jahn-Teller terms, subject of course to the presence of only a very small (or zero) isotope effect. 

Based on these direct experimental measurements, we conclude that the binding energy of the singlet polaron-excitons in conjugated polymers might be relatively small... 

We emphasize that the small value of the polaron-exciton binding energy results from a cancellation (indirect) of the electron-electron and electron-lattice contributions. This cancellation demonstrates the need for correlation effects to be taken into account when describing the excited state wavefunctions. 

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