Interband optical transitions in DNA-like systems

Abstract

The underlying band structure of the uniform DNA suggests the allowance of interband optical transitions. We consider such transitions in the uniform synthetic DNA, such as the poly(G)-poly(C) DNA, within a simple tight-binding model with a minimum set of parameters. We demonstrate that the helical conformation of the DNA strands results in unusual interband optical transitions all of which appear to be indirect in k space although the system has a direct band gap energy structure. Simple relationships of the optical gap and absorption linewidth to tight-binding model parameters are found. We study also the effect of disorder in base levels (relevant for the wet form of the DNA) on interband optical transitions.