Dynamic admittance of carbon nanotube-based molecular electronic devices and their equivalent electric circuit

Abstract

We use first-principles quantum mechanics to simulate the transient electrical response through carbon nanotube-based conductors under time-dependent bias voltages. The dynamic admittance and time-dependent charge distribution are reported and analyzed. We find that the electrical response of these two-terminal molecular devices can be mapped onto an equivalent classical electric circuit and that the switching time of these end-on carbon nanotube devices is only a few femtoseconds. This result is confirmed by studying the electric response of a simple two-site model device and is thus generalized to other two-terminal molecular electronic devices.

Time-dependent density functional theory for quantum transport

“…[2][3][4][5][6][7][8][9][10] As a formally rigorous and numerically tractable approach, TDDFT promises real-time simulations on ultrafast electron transport through realistic electronic devices or structures. In early attempts, finite source-device-drain systems were treated by the conventional TDDFT for isolated systems.…”

“…6 One of recent applications of the TDDFT-NEGF-EOM method was a simulation on the ultrafast transient current through a carbon nanotube based electronic device. It was found that the dynamic electronic response of the device can be mapped onto an equivalent classical electric circuit, 7,16 which would be useful for future design of functional devices.…”

“…Our previous simulations on realistic nanoelectronic devices 6,7 have demonstrated the numerical feasibility of our TDDFT-NEGF-EOM approach for open systems, while its accuracy is largely determined by the quality of approximated exchange-correlation (XC) functional which accounts for the many-particle effects, and that of dissipation functional which characterizes the dissipative interactions between the electronic device and electrodes. In our previous simulations we employed the adiabatic local density approximation 17 (ALDA) for the XC functional and the adiabatic wide-band limit 6 (AWBL) approximation for the dissipation functional.…”

Higher harmonics and ac transport from time dependent density functional theory

“…Do conventional organic molecules behave as classical capacitors or inductors, or does their ac response depend on frequency and chemistry in a non-trivial way? This question was already addressed by Fu and Dudley in the 1990s for the model system of a resonant tunneling diode [14], and recently, several groups presented DFT based calculations of ac conductances for realistic molecular junctions [15,16,17,18,19].…”

Alternating current response of carbon nanotubes with randomly distributed impurities

“…This is attributed to the fact that the kinetic inductance increases with the dwell time of electrons, which is due to the inertia of the electrons. 6 Investigations of the effect of contact between a pristine metallic CNT and metallic electrodes on the AC transport properties [7][8][9] have shown that the sub-terahertz frequency susceptance changes from an inductive response to a capacitive response with decreasing DC conductance. 8,9 This indicates that there is a correlation between the DC conductance and the subterahertz frequency susceptance.…”