Phonon induced dephasing

Presently there is no consensus whether or not resonant phonons play a dominant role in optical dephasing phenomena. Indeed the only clear example of resonant phonon-induced dephasing is the case of tetracene in p-terphenyl. ... 

We find that the LF in a QD dominated by phonon-induced dephasing processes leads to the appearance of regions with zero population and step-like transitions in the ROs for small pulse areas and relatively long pulse durations, in contrast to systems without LF effects, where ROs exhibit a damped sinusoidal behavior due to the the electron-phonon coupling for the parameters used here. 

MEG is intimately related to phonon-induced dephasing. Impact ionization assumes incoherent transitions from high-energy SE states to MEs. The loss of electronic coherence occurs by coupling to phonons and, in this case, should be faster than MEG. The dephasing mechanism " starts with a coherent superposition of single and ME states and associates MEG with dephasing of the... 

Phonon-induced pure dephasing/decoherence time for pairs of electronic states. Adapted from Ref. 43 (Copyright 2008 American Chemical Society). 

When, however, phonons of appropriate energy are available, transitions between the various electronic states are induced (spin-lattice relaxation). If the relaxation rate is of the same order of magnitude as the magnetic hyperfine frequency, dephasing of the original coherently forward-scattered waves occurs and a breakdown of the quantum-beat pattern is observed in the NFS spectrum. 

Dephasing is another important broadening process for spectral lines of adsorbates. Elastic collisions of phonons and conduction electrons with adsorbed atoms or molecules disrupt the phases of their induced dipole moments and thus provide surface-specific pathways for phase relaxation. If an adsorbed particle can be considered as a two-level system, both the lifetime of its excited state, T, and the dephasing time, T, contribute to the spectral linewidth 7 as ... 

Thirdly, the collision-induced Raman resonances can expand the application of Raman spectroscopy to situations where the conventional Raman susceptibility vanishes. Andrews et al., for example, have demonstrated that sharp vibrational transitions in an initially unpopulated excited electronic state of a molecule can be observed as extra four-wave mixing resonances, even though they cannot be observed in absorption because of rapid dephasing of the electronic transition. In these experiments pentacene molecules were doped in a benzoic acid crystal, and phonon scattering rather than collisions provided the dephasing mechanism. CARS of equally-populated ground state rotational levels in molecules would also become possible by observing collision-induced resonances. 

Electron phonon interactions induce two distinct processes in QDs dephasing and relaxation. Superposition of electronic states, created by the coulomb interaction during photoexdtation and subsequent time evolution, dephases into incoherent mixtures of states. Dephasing is ultrafast if it involves electronic states with substantially different energies and spatial densities. Examples of this include superposition of SEs and MEs and ground and excited states. ME fission into independent SEs occurs by dephasing that is much slower. This is because MEs are typically formed by SEs that are close in energy. 

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