Electron-phonon correction

Figure 5.27 (a) Vertex with no semiconductor electron-phonon correction and (b) the... 

Figure 5. Model spectra of a naked neutron star. The emitted spectrum with electron-phonon damping accounted for and Tsurf = 106 K. Left panel uniform surface temperature right panel meridional temperature variation. The dashed line is the blackbody at Tsurf and the dash-dotted line the blackbody which best-fits the calculated spectrum in the 0.1-2 keV range. The two models shown in each panel are computed for a dipole field Bp = 5 x 1013 G (upper solid curve) and Bp = 3 x 1013 G (lower solid curve). The spectra are at the star surface and no red-shift correction has been applied. From Turolla, Zane and Drake (2004).

Electron-phonon interaction in a semiconductor is the main factor for relaxation of a transferred electron. There are two different relaxation processes that decrease the efficiency of light conversion in a solar system (1) relaxation of an electron from a semiconductor conduction band to a valence band and (2) a backward electron transfer reaction. The forward and backward electron transfer processes have been already included in the tunneling interaction, HSm-qd, described by Eq. (108). However, the effect of SM e-ph interaction is important for the correct description of electron transfer in the SM-QD solar cell system. In the previous section, we have gradually considered different types of interactions in the quantum dot and obtained the exact expression for the photocurrent (128) where the exact nonequilibrium QD Green s functions determined from Eq. (127) have been used. However, in... 

When both electron-phonon and electron-electron interactions are included, in general one or the other dominates, with corrections due to the less important interaction becoming large near the transition region and using the experimental gap and bond alternation values for PA (which are not very accurately known, for reasons discussed below), it seems that trans-PA is near the transition, so that the SSH approach, although incomplete, is still qualitatively very fruitful [37,62,63]. 

The cause or causes of the opening of a gap in the band structure of trans-PA has been the subject of many theoretical papers and of much debate (see Chapter 11, Section IV.A and reviews and discussions in [17,146,147,181]). It would seem that electron-phonon and electron-election interactions are of comparable importance. If electron correlations are treated by adding a Hubbard on-site interaction term to the SSH Hamiltonian, the available experimental results for tram-PA are best accounted for by taking about equal values for the electron-phonon coupling X and for the Hubbard U. It might be that in other CPs the importance of electron correlations is greater. Note, however, that a U term (on-site interactions) is not enough to treat the correlations correctly, especially if excitons are to be studied (see the discussion of the PDA case above). 

If the scattering mechanism of the electrons is T-independent, , is constant and S T) becomes proportional to T [5.103]. Many-body effects, on the other hand, may cause non-linearities at low temperatures due to electron-phonon mass-enhancement effects, giving S(T) = [1 + A(T)] Sb(T) [5.104]. Sb is now the bare thermopower of (5.19) without mass-enhancement. Higher correction terms have been proposed by Kaiser [5.105]. The resistivity should not be influenced by mass-enhancement effects [5.106]. 

The c ontrol o f p honon t emperature i n e lectron-phonon c oupling measurements i s critical for a correct estimation of the electron-phonon coupling constant. In our experiment an additional electrically isolated S-Sm-S thermometer was placed near the Si film. Below IK the electron-phonon thermal resistance in silicon is considerably larger than the Kapitza resistance between Si film and the silicon oxide layer, and therefore the S-Sm-S thermometer next to the silicon film was assumed to be at approximately the same temperature as the phonon system in the silicon film. 

Fig. 7. Resistivity data of YbAls and YbAl2. The solid lines give the experimentally obtained Ap p vs. T curves corrected for residual and electron-phonon scattering contributions. The dotted lines show the estimated contributions due to spin-disorder scattering by the Yb magnetic moments described by the second term of eq. (16). The dashed lines show the estimated contribution connected with scattering processes on Yb virtual bound states which is described by the first term of eq. (16) (Havinga et al., 1973).

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