1,721,057 research outputs found
Band-like motion and mobility saturation in organic molecular semiconductors
No full textWe analyze a model that accounts for the inherently large thermal lattice fluctuations associated with the weak van der Waals intermolecular bonding in crystalline organic semiconductors. In these materials the charge mobility generally exhibits a “metalliclike” power-law behavior, with no sign of thermally activated hopping characteristic of carrier self-localization, despite apparent mean free paths comparable to or lower than the intermolecular spacing. Our results show that such a puzzling transport regime can be understood from the simultaneous presence of band carriers and incoherent states that are dynamically localized by the thermal lattice disorder
Signatures of polaronic charge ordering in optical and dc conductivity using dynamical mean field theory
No full textOptical properties of small polarons from dynamical mean-field theory
No full textThe optical properties of polarons are studied in the framework of
the Holstein model by applying the dynamical mean-field theory. This approach
allows to enlighten important quantitative and qualitative deviations from the
limiting treatments of small polaron theory, that should be considered when
interpreting experimental data. In the antiadiabatic regime, accounting on
the same footing for a finite phonon frequency and a finite electron
bandwidth allows to address the evolution of the optical absorption away from
the well-understood molecular limit. It is shown that the width of the
multiphonon peaks in the optical spectra depends on the temperature and on the
frequency in a way that contradicts the commonly accepted results, most
notably in the strong coupling case. In the adiabatic regime, on the other
hand, the present method allows to identify a wide range of parameters of
experimental interest, where the electron bandwidth is comparable or larger
tha..
Spectral properties and isotope effect in strongly interacting systems: Mott-Hubbard insulator versus polaronic semiconductor
No full textWe study the electronic spectral properties in two examples of strongly interacting systems: A Mott-Hubbard insulator with additional electron-boson interactions, and a polaronic semiconductor. An approximate unified framework is developed for the high energy part of the spectrum, in which the electrons move in a random field determined by the interplay between magnetic and bosonic fluctuations. When the boson under consideration is a lattice vibration, the resulting isotope effect on the spectral properties is similar in both cases, being strongly temperature and energy dependent, in qualitative agreement with recent photoemission experiments in the cuprates
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