Absence of extended states in a ladder model of DNA

TL;DR

This paper investigates carrier transport in a DNA ladder model, showing that natural base pairing correlations do not lead to extended electronic states, challenging previous claims.

Contribution

It provides an analytical and numerical analysis demonstrating the absence of extended states in a realistic DNA model with natural base pairing.

Findings

Natural base pairing does not produce extended states.

Carrier states remain localized despite DNA correlations.

Previous claims of extended states are contradicted.

Abstract

We consider a ladder model of DNA for describing carrier transport in a fully coherent regime through finite segments. A single orbital is associated to each base, and both interstrand and intrastrand overlaps are considered within the nearest-neighbor approximation. Conduction through the sugar-phosphate backbone is neglected. We study analytically and numerically the spatial extend of the corresponding states by means of the Landauer and Lyapunov exponents. We conclude that intrinsic-DNA correlations, arising from the natural base pairing, does not suffice to observe extended states, in contrast to previous claims.