Bound states in<i>ab initio</i>approaches to quantum transport: A time-dependent formulation

Stefanucci, Gianluca

doi:10.1103/physrevb.75.195115

Cited by 89 publications

(90 citation statements)

References 48 publications

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“…We mention that it has recently been shown in the time-dependent NEGF framework that the presence of bound states can affect the long time behavior of the current in the noninteracting case. 41 …”

Section: Bound States and The ⌬ Termmentioning

confidence: 99%

ConservingGWscheme for nonequilibrium quantum transport in molecular contacts

2008

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We give a detailed presentation of our recent scheme to include correlation effects in molecular transport calculations using the nonequilibrium Keldysh formalism. The scheme is general and can be used with any quasiparticle self-energy, but for practical reasons, we mainly specialize to the so-called GW self-energy, widely used to describe the quasiparticle band structures and spectroscopic properties of extended and lowdimensional systems. We restrict the GW self-energy to a finite, central region containing the molecule, and we describe the leads by density functional theory ͑DFT͒. A minimal basis of maximally localized Wannier functions is applied both in the central GW region and the leads. The importance of using a conserving, i.e., fully self-consistent, GW self-energy is demonstrated both analytically and numerically. We introduce an effective spin-dependent interaction which automatically reduces self-interaction errors to all orders in the interaction. The scheme is applied to the Anderson model in and out of equilibrium. In equilibrium at zero temperature, we find that GW describes the Kondo resonance fairly well for intermediate interaction strengths. Out of equilibrium, we demonstrate that the one-shot G 0 W 0 approximation can produce severe errors, in particular, at high bias. Finally, we consider a benzene molecule between featureless leads. It is found that the molecule's highest occupied molecular orbital-lowest unoccupied molecular orbital gap as calculated in GW is significantly reduced as the coupling to the leads is increased, reflecting the more efficient screening in the strongly coupled junction. For the I-V characteristics of the junction, we find that Hartree-Fock ͑HF͒ and G 0 W 0 ͓G HF ͔ yield results closer to GW than does DFT and G 0 W 0 ͓G DFT ͔. This is explained in terms of selfinteraction effects and lifetime reduction due to electron-electron interactions.

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Section: Bound States and The ⌬ Termmentioning

confidence: 99%

ConservingGWscheme for nonequilibrium quantum transport in molecular contacts

2008

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“…41,42 In such cases, the Landauer-Büttiker formula becomes inadequate for describing the long-time limit of transient current. In fact, these bound states are physically decoupled with the rest of composite system, and form an isolated subsystem.…”

Section: Discussionmentioning

confidence: 99%

Time-dependent density functional theory for quantum transport

2013

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Based on our earlier works [Phys. Rev. B 75, 195127 (2007) & J. Chem. Phys. 128, 234703 (2008], we propose a formally exact and numerically convenient approach to simulate time-dependent quantum transport from first-principles. The proposed approach combines time-dependent density functional theory with quantum dissipation theory, and results in a useful tool for studying transient dynamics of electronic systems. Within the proposed exact theoretical framework, we construct a number of practical schemes for simulating realistic systems such as nanoscopic electronic devices. Computational cost of each scheme is analyzed, with the expected level of accuracy discussed. As a demonstration, a simulation based on the adiabatic wide-band limit approximation scheme is carried out to characterize the transient current response of a carbon nanotube based electronic device under time-dependent external voltages.

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“…[51] (see also Ref. [53]); they are due to a difficulty in maintaining the occupation of the bound state at the correct equilibrium value. The simple model we have used for the numerical calculations has no interactions between electrons and no phonons which can lead to inelastic scattering processes and thereby maintain the occupation of the bound state at a value dictated by the Fermi function.…”

Section: Discussionmentioning

confidence: 99%

Nonadiabatic charge pumping in a one-dimensional system of noninteracting electrons by an oscillating potential

Agarwal

Sen

2007

Phys. Rev. B

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Using a tight-binding model, we study one-parameter charge pumping in a one-dimensional system of non-interacting electrons. An oscillating potential is applied at one site while a static potential is applied in a different region. Using Floquet scattering theory, we calculate the current up to second order in the oscillation amplitude and exactly in the oscillation frequency. For low frequency, the charge pumped per cycle is proportional to the frequency and therefore vanishes in the adiabatic limit. If the static potential has a bound state, we find that such a state has a significant effect on the pumped charge if the oscillating potential can excite the bound state into the continuum states or vice versa. Finally, we use the equation of motion for the density matrix to numerically compute the pumped current for any value of the amplitude and frequency. The numerical results confirm the unusual effect of a bound state.

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Bound states inab initioapproaches to quantum transport: A time-dependent formulation

Cited by 89 publications

References 48 publications

ConservingGWscheme for nonequilibrium quantum transport in molecular contacts

ConservingGWscheme for nonequilibrium quantum transport in molecular contacts

Time-dependent density functional theory for quantum transport

Nonadiabatic charge pumping in a one-dimensional system of noninteracting electrons by an oscillating potential

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