Acoustic deformations

The essential difference between the SWAP and the Davydov Soliton (apart from numerical matters) lies in the effect of the acoustic deformation in the former it changes the electron inter site transfer energy, whereas in the latter it changes the on site exciton vibrational energy. The difference between on site and inter site will not show up for polarons larger than the lattice spacing. 

The stress we lay on the difference between optic and acoustic deformation is a reaction to the enormous literature on exclusively optic polarons in conjugated polymers. Yet as the Davydov Soliton and SWAP show, it is the acoustic deformation which dominates the motion of the polaron. In so far as it is motion which is the essential quality of a Soliton, it is the Acoustic deformation which it is essential to consider. In reality... 

In this paper, we present the lateral size dependence of Huang-Rhys factors for the QW heterostructures with the localized quasi-2D excitonic states. The Huang-Rhys factor is a quantity representing the coupling strength of a localized particle with phonons [4]. All exciton-phonon interaction mechanisms are analyzed. They are the polar optic (Froehlich) interaction, the optic deformation potential, the acoustic deformation potential, and the acoustic piezoelectric interaction. We would... 

The acoustic Huang-Rhys factor for localized 2D-excitons is shown in Fig. 1(b). The acoustic deformation potential interaction totally prevails over the acoustic peizoelectric interaction. The total acoustic Huang-Rhys factor is 1 and increases with the decreasing QD size. This indicates rather strong exciton-acoustic-phonon coupling which further enhances with the decrease of the QD lateral size. 

However, this order of parameter hides the acoustic deformations (compressions and expansions) of the lattice. Sound waves are therefore nearly invisible when the geometry is described by y . To emphasize such deformations we introduce an acoustic order parameter given by... 

It is clear from the topmost graph in Figure 2.5 that the static polaron contains an acoustic deformation, more specifically, a contraction of the chain (z <0). When an electric field lower than... 

The change in the geometry associated with the polaron moving at supersoiuc velocities also affects the electronic structure of the system. The transition fi-om below to above the sound velocity is clearly coupled to the phonons, i.e., the energy associated with the acoustic deformation of the static polaron is... 

In ID the lattice deforms around the electron and loced.ises the electron to form a polaron. The ii portant deformation is acoustic, in udiich the density of the lattice changes optic deformations occur also but are not important in the polaron motion. The mathematical description of the polaron is like that of solitary waves. The Solitary wave Acoustic Polaron (SWAP) has a very large effective mass its kinetic velocity is small. Horeover it cannot move at a velocity greater than S as its kinetic velocity approaches S the acoustic deformation increases and the SNAP mass increases. In addition back scattering is very rare. So the SWAP kinetic and drift velocities are equal. 

Topography has already proved to be a suitable technique for studying magnetic domain formation or acoustic deformation down to time-scales of milliseconds. 

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