Strong electron-phonon coupling theory

Another approximation scheme (strong electron-phonon coupling theory) starts from the opposite assumption that the electronic coupling Vei is a small perturbation, i.e., the molecular crystal can be seen as a collection of isolated molecules. Molecule j is deformed by the presence of a carrier and the set of vibronic states localized on j form the basis for a transformed Hamiltonian [69, 71,72]. In second quantization the transformed Hamiltonian can be written as... 

Superconducting tunneling and inelastic neutron scattering are techniques for determining phonon spectra. McMillan s strong electron-phonon coupling theory yields an equation for 7 ... 

Defect recombination is therefore primarily non-radiative. The standard theories of non-radiative transitions are based on the multiphonon processes described in Section 8.1.2. A temperature-independent capture cross-section of about 10 cm" is characteristic of a defect state with a strong electron-phonon coupling (see Fig. 8.6). 

We have thus found that in this high temperature, strong electron-phonon coupling limit the electronic transition is dominated by the lowest crossing point of the two potential surfaces, that is, the system chooses this pathway for the electronic transition. It is remarkable that this result, with a strong characteristic of classical rate theory, was obtained as a limiting fonn of the quantum golden-rule expression for the transition rate. Equation (12.69) was first derived by Marcus in the context of electron transfer theory (Chapter 16). 

In summary, the experimentally obtained FS topology of the k phase is principally in good agreement with the predicted band structure. Some of the salts exhibit an extreme 2D electronic structure, even by standards of ET compounds. Especially for /t-(ET)2l3 strong deviations from the 3D Lifshitz-Kosevich theory are observed. On the other hand, the dHvA signal of At-(ET)2Cu(NCS)2 is fully compatible with the 3D theory and even the extraction of the electron-phonon coupling constant was possible. The effective cyclotron masses for the MB orbit are 3.9 me for the first and 7me for the latter salt. How far this reflects the different TcS of these two compounds needs further investigation. 

The physics of exciton ST has many features in common with electron (hole) ST. Therefore, the methods and results of the theory of electron ST have been widely used in the development of the theory of exciton ST. The effects of strong exciton-phonon coupling in organic crystals and the possibility of exciton ST were discussed in the papers by Peierls (35), Frenkel (36), and Davydov (37). 

On the contrary, when electron-phonon coupling is strong and at high temperatures, the Marcus theory is preferred [52], given here under its so-called symmetrical jump rate form ... 

PSHB) results were obtained from fluorescence (F) and fluorescence excitation (E) on post etiolated as well as green leaves in 24, 25. The two level system theory developed for spectral HB is summarised in 26 moreover strong linear electron-phonon coupling is discussed in 27. ... 

---