Bloch oscillations in organic and inorganic polymers

Spectral Analysis of Bloch-Like Oscillations in Conjugated Polymers

We present a spectrum investigation of the behavior of dissociated polarons under high electric fields in conjugated polymers. The study employs the Su-Schrieffer-Heeger model along with nonadiabatic molecular dynamics and frequency-domain analysis methods to analyze the Bloch-like oscillations. It is found that the fundamental frequencies of the current density agree well with the theoretical Bloch frequencies of the perfect crystals. The electron-phonon coupling is a key factor in inducing the deviation between the Bloch-like oscillation behavior in conjugated polymers and that in perfect superlattices. Moreover, the increase in lattice thermal fluctuation is not conducive to the maintenance of Bloch-like oscillation behavior in conjugated polymers.

The superposed electric field effect on the charge transport and polaron formation in molecular crystals

We study the polaron formation and its mobility in a one-dimensional molecular crystal subjected to superposed static and harmonic electric fields. Such molecular chain exhibits intermolecular vibrational degrees of freedom, which makes the carrier-lattice interaction an important parameter of the system. By exploring field settings in which the preferential transport occurs, we show the existence of different small polaron formations, including those that travel close to the sound velocity or that are stationary by self-trapping. Electric fields magnitudes and carrier-lattice coupling have also been analyzed, which allowed to show a phase diagram that describes the existing regimes. In addition to thresholds between the mobile and stationary polaron regimes, this phase diagram unveils an unusual aspect: a metastable polaron formation.

Polaron dynamics in oligoacene stacks

The dynamical properties of polarons in organic molecular crystals are numerically studied in the framework of an one-dimensional Holstein-Peierls approach that includes lattice relaxation. Particularly, the present study is aimed at designing a tight-binding Hamiltonian that can address the charge transport mechanism in model oligoacene stacks. Our findings show that the definition of a particular oligoacene system depends strictly on the employed set of parameters. The usefulness of this methodology is highlighted by analyzing the polaron's saturation velocity and, consequently, its stability in the presence of a damping term and substantially high electric field strengths. Importantly, these results may be useful for the designing of novel materials to be employed in the field of molecular electronics.