(Invited) Intermediate Tunnelling-Hopping Regime in DNA Charge Transport

Charge transport in molecular systems, including DNA, is related to many basic chemical and biological processes, and critical to device applications with molecules. This important phenomenon is often described as either coherent tunneling over a short distance or incoherent hopping over a long distance. Here we show evidence of an intermediate regime where coherent and incoherent processes coexist in dsDNA. We measure charge transport in single DNA molecules bridged to two electrodes as a function of DNA sequence and length. The resistance of DNA in general increases linearly with length, as expected for incoherent hopping. However, for DNA sequences with stacked guanine-cytosine (GC) base pairs, a periodic oscillation superimposes on the linear length dependence, indicating partial coherent transport. The result is supported by the finding of strong delocalization of the highest occupied molecular orbitals of GC by theoretical simulation and modeled based on the Büttiker theory of partial coherent charge transport.