Exciton electron interaction

We present a detailed calculation of the transition temperature of a model, filamentary excitonic superconductor. The proposed structure consists of a linear chain of transition-metal atoms to which is complexed a ligand system of highly polarizable dye molecules. The model is discussed in the light of recent developments in our understanding of one-dimensional metals. We show that for the structure proposed, the momentum dependence of the exciton interaction results in the superconducting state being favoured over the Peierls state, and in vertex corrections to the electron-exciton interaction which are small. The calculation of the transition temperature is based on what we believe to be reasonable estimates of the strength of the excitonic interaction, Coulomb repulsion and band structure. 

The NDCPA seems to be a very reasonable way to treat the properties of both electrons and excitons interacting with phonons with dispersion. In principal, the NDCPA can be applied to a system of the Hamiltonian with the electron(exciton)-phonon coupling terms of arbitrary structure. The NDCPA results in an algorithm which can be effectively treated numerically (for example, iteratively). The application of the NDCPA is not restricted to the... 

Not all sensitized photochemical reactions occur by electronic energy transfer. Schenck<77,78) has proposed that many sensitized photoreactions involve a sensitizer-substrate complex. The nature of this interaction could vary from case to case. At one extreme this interaction could involve a-bond formation and at the other extreme involve loose charge transfer or exciton interaction (exciplex formation). The Schenck mechanism for a photosensitized reaction is illustrated by the following hypothetical reaction ... 

Optical Absorption Spectra and Electronic Structure The optical spectra of all the doubledeckers are listed in Table I, On first glance, Ce(0EP)2 has a "normal" spectrum (7), However, the spectrum shows extra bands and therefore should be called "hyper", A small band appears at 467 nm (maybe a ligand-to-metal charge transfer band), and broad features extend far into the near infrared (NIR), The latter absorption may be due to exciton interactions. Contrary to the known rare earth monoporphyrins (7), it has been shown for the closely related cerium(IV)... 

Triad 25 is another example of this general type [75]. As was the case with the previously discussed triads 15—18, the absorption spectrum of 25 indicates some degree of excitonic interaction between the porphyrins. The fluorescence quantum yield of 25 is 5 5 x 10-6, which indicates efficient quenching of the porphyrin singlet states, presumably by electron transfer. No information concerning the lifetime of any charge separated state was presented, but one would predict that it would be extremely short. 

Exciton interaction , commonly used in squaraine literature, describes the effect of electronic interactions between squaraine pairs, although it is strictly speaking a pseudo-exdmeric interaction. 

Linear response polarizability theory of spectral bandshapes was applied to the numerical analysis of the chiroptical spectra obtained for DNA-acridine orange complexes [85]. After analysis of various models of conformation, it was concluded that a dimer-pairs repeating sequence model was best able to account for the observed spectral trends. In another work, the CD induced in the same band system was studied at several ionic strengths [86]. The spectra were able to be interpreted in terms of the long-axis-polarized electronic transitions of the dyes, with the induced CD being attributed to intercalated and non-intercalated dye species superimposed by degenerate vibronic exciton interactions between these. 

The electron-phonon interactions also influence the linewidth of the interband and exciton transitions. This temperature-dependent homogeneous... 

In this section we study the interaction of a branch of electronic excitons with a mode of vibrations and phonons. The parameters in this model are the dispersion width 2B of the excitonic band, the average energy quantum hQ0 of the vibration, the coupling intensity, and the temperature. According to the ordering of these parameters, the system shows very different behavior, whose general treatment is beyond the scope of this section. We restrict ourselves to the usual cases that are relevant to the first singlet exciton of the anthracene crystal and to its absorption and emission mechanisms. 

The eigenstates of h are molecular vibronic states B and J are respectively operators and undressed excitonic interactions, purely electronic. 

Excitation of the polymer creates one electron and a hole on the chain. This effect is particularly important when the electron-hole interactions are strong. Coulomb attraction keeps them together and we consider the two opposite charges as a bound electron-hole pair. An exciton (Fig. 1.11) is named according to its delocalisation. If it is localised, it is called a Frenkel exciton and, if it is delocalised, i.e., it extends over many molecular units, it is a Mott-Wannier type of exciton. ... 

The elementary excitations of a conjugated polymer chain can be described within the mono-electronic approach as electron and hole quasiparticles [74] in a one-dimensional band structure, possibly weakly bound into extended Wannier-type excitons [71,75]. Within this framework, electron-phonon interactions lead to a peculiar family of exotic excitations including solitons, polarons, polaron pairs and bipolarons. In many cases, however, disorder is so significant that the polymer films are better described as an ensemble of relatively short conjugated segments [76], essentially behaving... 

A QD Hamiltonian includes both Coulomb and electron-phonon interactions. Apparently, the phonon modes (denoted as QD) in the quantum dot are different from the semiconductor ones. The electron-phonon interaction determines relaxation processes in quantum dot (hot electrons or excitons). Thus, the QD Hamiltonian yields... 

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