AbstractWe employ Real-Time Time-Dependent Density Functional Theory to study hole oscillations within a B-DNA monomer (one base pair) or dimer (two base pairs). Placing the hole initially at any of the bases which make up a base pair, results in THz oscillations, albeit of negligible amplitude. Placing the hole initially at any of the base pairs which make up a dimer is more interesting: For dimers made of identical monomers, we predict oscillations with frequencies in the range f≈ 20–40 THz, with a maximum transfer percentage close to 1. For dimers made of different monomers, f≈ 80–400 THz, but with very small or small maximum transfer percentage. We compare our results with those obtained recently via our Tight-Binding approaches and find that they are in good agreement.

We study the frequency content of an extra carrier oscillation along characteristic periodic B-DNA polymers made of N monomers. We employ two variants of the Tight-Binding approach, a wire model and an extended ladder model including diagonal hoppings. In the former, the site is a monomer, i.e., a base pair, while, in the latter, the site is a base. Initially, we focus on the Fourier Spectra of the probabilities to find the extra carrier at each monomer, having placed it at time zero at a specific monomer. Using the Fourier amplitude of each component of the frequency spectrum, we define the weighted mean frequency (WMF) for each site, a measure of its frequency content. To obtain a measure of the overall frequency content of carrier oscillations in the polymer, we define the total weighted mean frequency (TWMF), averaging the WMFs of all sites weighting over the probabilities of finding the extra carrier at each site. The frequency content is generally in the THz domain. Finally, we also give an example of an aperiodic sequence, the (A, T) Cantor dust.

Atomic carbon wires represent the ultimate one-atom-thick one-dimensional structure. We use a Tight-binding (TB) approach to determine the electronic structure of polyynic and cumulenic carbynes, in terms of their dispersion relations (for cyclic boundaries), eigenspectra (for fixed boundaries) and density of states (DOS). We further derive the transmission coefficient at zero-bias by attaching the carbynes to semi-infinite metallic leads, and demonstrate the effect of the coupling strength and asymmetry to the transparency of the system to incident carriers. Finally, we determine the current–voltage (I–V) characteristics of carbynes and study the effect of factors such as the weakening of the coupling of the system to one of the leads, the relative position of the Fermi levels of the carbyne and the leads, the leads' bandwidth and, finally, the difference in the energy structure between the leads. Our results confirm and reproduce some of the most recent experimental findings.