From Exhaustive Simulations to Key Principles in DNA Nanoelectronics

Abstract

Charge transfer can take place along double helical DNA over distances as long as 30 nanometers. However, given the active role of the thermal environment surrounding charge carriers in DNA, physical mechanisms driving the transfer process are highly debated. Moreover, the overall potential of DNA to act as a conducting material in nanoelectronic circuits is questionable. Here, we identify key principles in DNA nanoelectronics by performing an exhaustive computational study. The electronic structure of double-stranded DNA is described with a coarse-grained model. The dynamics of the molecular system and its environment is taken into account using a quantum scattering method, mimicking incoherent, elastic and inelastic effects. By analyzing all possible sequences with 3 to 7 base pairs, we identify fundamental principles in DNA nanoelectronics: The environment crucially influences the electrical conductance of DNA, and the majority of sequences conduct via a mixed, coherent-incoherent mechanism. Likewise, the metal-molecule coupling and the gateway states play significant roles in the transport behavior. While most sequences analyzed here are exposed to be rather poor electrical conductors, we identify exceptional DNA molecules, which we predict to be excellent and robust conductors of electric current over a wide range of physical conditions.

Machine Learning Prediction of DNA Charge Transport

“…Most importantly, as reported in Ref. 31 , while we can identify ballistic (green) and ohmic (black) conductors, most molecules display an in-between behavior, G ∝ γ α d with 0 α 1 at high electronic temperature. These sequences conduct via an intermediate, coherent-incoherent mechanism.…”

“…As we discuss in Ref. 31 , we identify in this figure different families of molecules: good (G = 1 − 0.01 G 0 ), poor (G < 10 −10 G 0 ), and intermediate conductors (G = 10 −2 −10 −6 G 0 ). Here, G 0 = e 2 /h is the quantum of conductance per spin species, with the electron charge e and Planck's constant h. Good conductors (panel a3) are only mildly affected by the environment showing a quantum-wire properties; poor conductors (panel a1) enjoy a dramatic enhancement of their conductance, assisted by the environment, demonstrating a tunneling-to-hopping crossover.…”

“…With the goal to describe charge transport in 1-5 nm long DNA, identify central transport mechanisms, and pinpoint exceptionally good or poor DNA conductors, we recently performed extensive conductance calculations of metal-molecule-metal DNA junctions 31 . In our scheme, the electronic structure of the double helix is described with a coarse grained model 47,48 , and the electrical conduction is calculated with a quantum scattering technique, the Landauer-Büttiker's probe (LBP) method 32,33 .…”

“…Here, G 0 = e 2 /h is the quantum of conductance per spin species, with the electron charge e and Planck's constant h. Good conductors (panel a3) are only mildly affected by the environment showing a quantum-wire properties; poor conductors (panel a1) enjoy a dramatic enhancement of their conductance, assisted by the environment, demonstrating a tunneling-to-hopping crossover. Nevertheless, the majority of the sequences cannot be categorized as tunneling/ohmic/ballistic conductors (panel a2), and their conductance under environmental effects largely depends on whether they have a local cluster of identical bases 31 .…”

Vibronic dephasing model for coherent-to-incoherent crossover in DNA

“…These structures are double-stranded and self-complementary. We follow the idea of previous authors 40, [44][45][46][47][48] and model these structures by using a next neighbor tight-binding (TB) ladder models as depicted in Fig. 2 (gray lines).…”