Time-dependent density-functional theory for open systems

Abstract

By introducing the self-energy density functionals for the dissipative interactions between the reduced system and its environment, we develop a time-dependent density-functional theory formalism based on an equation of motion for the Kohn-Sham reduced single-electron density matrix of the reduced system. Two approximate schemes are proposed for the self-energy density functionals, the complete second order approximation and the wide-band limit approximation. A numerical method based on the wide-band limit approximation is subsequently developed and implemented to simulate the steady and transient current through various realistic molecular devices. Simulation results are presented and discussed.

Time-dependent density functional theory for quantum transport

“…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.…”

“…Our RSDM based TDDFT-EOM has been combined with the Keldysh's nonequilibrium Green's Function (NEGF) formalism, the resulting TDDFT-NEGF-EOM approach has been applied successfully to exploit transient electronic dynamics in realistic molecular electronic devices. 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.…”

“…4,5 We have also developed an accurate numerical scheme, 6 based on a closed equation of motion (EOM) for the Kohn-Sham (KS) RSDM. Our RSDM based TDDFT-EOM has been combined with the Keldysh's nonequilibrium Green's Function (NEGF) formalism, the resulting TDDFT-NEGF-EOM approach has been applied successfully to exploit transient electronic dynamics in realistic molecular electronic devices.…”

“…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. Despite the success, the ALDA approximation is expected to become inadequate for addressing transient dynamics of open electronic systems in circumstances where electron correlations dominate.…”

“…[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.…”