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[en] A system of polaritons interacting with a two-level atom placed within a frequency dispersive medium is proved to be integrable, despite a non-local effective polariton-polariton coupling. The two-polariton factorization of a many-polariton scattering process is hidden and is manifested only in the limit of large inter polariton separations. (author). Letter-to-the-editor
[en] We discuss memory effects in the conductance of hopping insulators due to slow rearrangements of many-electron clusters leading to formation of polarons close to the electron hopping sites. An abrupt change in the gate voltage and corresponding shift of the chemical potential change populations of the hopping sites, which then slowly relax due to rearrangements of the clusters. As a result, the density of hopping states becomes time dependent on a scale relevant to rearrangement of the structural defects leading to the excess time-dependent conductivity.
[en] We carry out a comprehensive theoretical and experimental study of charge injection in poly(3-hexylthiophene) (P3HT) to determine the most likely scenario for metal-insulator transition in this system. We calculate the optical-absorption frequencies corresponding to a polaron and a bipolaron lattice in P3HT. We also analyze the electronic excitations for three possible scenarios under which a first- or a second-order metal-insulator transition can occur in doped P3HT. These theoretical scenarios are compared with data from infrared absorption spectroscopy on P3HT thin-film field-effect transistors (FETs). Our measurements and theoretical predictions suggest that charge-induced localized states in P3HT FETs are bipolarons and that the highest doping level achieved in our experiments approaches that required for a first-order metal-insulator transition
[en] We discuss memory effects in the conductance of hopping insulators due to slow rearrangements of structural defects leading to the formation of polarons close to the electron hopping states. An abrupt change in the gate voltage and corresponding shift of the chemical potential change the populations of the hopping sites, which then slowly relax due to rearrangements of structural defects reducing the density of states. As a result, the density of the hopping states becomes time dependent on a scale relevant to the rearrangement of the structural defects, leading to excess time-dependent conductivity.