An advanced two-dimensional tight-binding model including the next nearest-neighbor effects for quantum mechanical electron transport through double-stranded DNA molecules is proposed. Considering the next nearest-neighbor hopping strengths between sites gives a more rational and realistic model for the electron path-way through DNA molecules. We show higher overall transmission and enhanced current for a 30 base-pair poly(G)–poly(C) DNA molecule with the inclusion of diagonal electron hopping between the sites. In addition, an optimum condition of the contact hopping strength and Fermi energy to obtain the maximum current for the system is demonstrated. Finally, we present the current-voltage characteristics showing a transition from a semiconductor-like to a metal-like DNA molecule with the variation of the Fermi energy.

We utilize a two-dimensional four-channel DNA model, with a tight-binding (TB) Hamiltonian, and investigate the temperature and the magnetic field dependence of the transport behavior of a short DNA molecule. Random variation of the hopping integrals due to the thermal structural disorder, which partially destroy phase coherence of electrons and reduce quantum interference, leads to a reduction of the localization length and causes suppressed overall transmission. We also incorporate a variation of magnetic field flux density into the hopping integrals as a phase factor and observe Aharonov-Bohm (AB) oscillations in the transmission. It is shown that for non-zero magnetic flux, the transmission zero leaves the real-energy axis and moves up into the complex-energy plane. We also point out that the hydrogen bonds between the base pair with flux variations play a role to determine the periodicity of AB oscillations in the transmission.

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