First-principles calculation of current density in molecular devices

Zhang, Lei; Wang, Bin; Wang, Jian

doi:10.1103/physrevb.84.115412

Cited by 20 publications

(22 citation statements)

References 40 publications

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“…In the first-principles calculations, the current density may be redefined by adding the contribution of the nonlocal potential, to conserve the current. 33…”

Section: B Initial Values and Numerical Integration In Time Domainmentioning

confidence: 99%

Time-dependent quantum transport: An efficient method based on Liouville-von-Neumann equation for single-electron density matrix

Xie

Jiang

Tian

et al. 2012

The Journal of Chemical Physics

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Basing on our hierarchical equations of motion for time-dependent quantum transport [X. Zheng, G. H. Chen, Y. Mo, S. K. Koo, H. Tian, C. Y. Yam, and Y. J. Yan, J. Chem. Phys. 133, 114101 (2010)], we develop an efficient and accurate numerical algorithm to solve the Liouville-von-Neumann equation. We solve the real-time evolution of the reduced single-electron density matrix at the tight-binding level. Calculations are carried out to simulate the transient current through a linear chain of atoms, with each represented by a single orbital. The self-energy matrix is expanded in terms of multiple Lorentzian functions, and the Fermi distribution function is evaluated via the Padè spectrum decomposition. This Lorentzian-Padè decomposition scheme is employed to simulate the transient current. With sufficient Lorentzian functions used to fit the self-energy matrices, we show that the lead spectral function and the dynamics response can be treated accurately. Compared to the conventional master equation approaches, our method is much more efficient as the computational time scales cubically with the system size and linearly with the simulation time. As a result, the simulations of the transient currents through systems containing up to one hundred of atoms have been carried out. As density functional theory is also an effective one-particle theory, the Lorentzian-Padè decomposition scheme developed here can be generalized for first-principles simulation of realistic systems.

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“…In the first-principles calculations, the current density may be redefined by adding the contribution of the nonlocal potential, to conserve the current. 33…”

Section: B Initial Values and Numerical Integration In Time Domainmentioning

confidence: 99%

Time-dependent quantum transport: An efficient method based on Liouville-von-Neumann equation for single-electron density matrix

Xie

Jiang

Tian

et al. 2012

The Journal of Chemical Physics

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“…Thirdly, we then calculate the nonlocal electron density using Eq. (32) and the nonlocal current density can be obtained from Eqs. (12) and (13).…”

Section: Numerical Calculation Of Ac Current Densitymentioning

confidence: 99%

“…Notice that the current density is defined in real space, the transformation from the orbital space to the real space should be done as in Ref. 32.…”

Section: Numerical Calculation Of Ac Current Densitymentioning

confidence: 99%

First-principles investigation of alternating current density distribution in molecular devices

Zhang

Wang

2012

Phys. Rev. B

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Using the nonequilibrium Green's function (NEGF) formalism, we derive the current density formula for ac quantum transport by including the self-consistent Coulomb interaction. It is well known that the Coulomb interaction is very important in determining ac current in nanostructures. As pointed out by Büttiker that the Coulomb interaction must be included to conserve the ac current. Theoretically, the displacement current can be accounted for by including a self-consistent Hartree term in the Hamiltonian as well as the exchange and correlation term while the ac current is calculated from particle current, i.e., Î α (t) = q dN α /dt whereN α is the number operator of the α lead. For the ac current density, however, the Coulomb interaction contributes in two ways. As the case of ac current, the self-consistent Coulomb interaction has to be included in the conventional particle current density. In addition, we have to consider the displacement current density explicitly, which is proportional to the time derivative of displacement field. Once the ac current density is obtained, one can calculate the ac current by integrating it over a cross-section area along the transport direction. It is shown that ac current obtained from the total ac current density is conserved and equal to that calculated directly from the lead using NEGF theory. We have applied our formalism to calculate ac current density for nanodevices by combining the density functional theory (DFT) with NEGF theory. Specifically, we have calculated the ac current density to the first order of frequency in a molecular device Al-C 4-Al from first principles. It is found that Al-C 4-Al system exhibits inductive-like behavior under ac bias in the low-frequency limit. Furthermore, nonequilibrium charge distribution is obtained that enables us to study electrochemical capacitance of the molecular devices.

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“…define the extended current in a different way from Refs. [27,28], and take into account the possibility of adding to it a solenoidal component. The correct definition of the physical current is still an open question, also regarding the dissipation properties of the non-local part: should the latter be interpreted as a "virtual" current or as a real current with real dissipation?…”

Section: Introductionmentioning

confidence: 99%

High-Frequency Electromagnetic Emission from Non-Local Wavefunctions

Modanese

2019

Applied Sciences

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In systems with non-local potentials or other kinds of non-locality, the Landauer-Büttiker formula of quantum transport leads to replace the usual gauge-invariant current density J with a current J ext which has a non-local part and coincides with the current of the extended Aharonov-Bohm electrodynamics. It follows that the electromagnetic field generated by this current can have some peculiar properties, and in particular the electric field of an oscillating dipole can have a long-range longitudinal component. The calculation is complex because it requires the evaluation of double-retarded integrals. We report the outcome of some numerical integrations with specific parameters for the source: dipole length ∼ 10 −7 cm, frequency 10 GHz. The resulting longitudinal field E L turns out to be of the order of 10 2 to 10 3 times larger than the transverse component (only for the non-local part of the current). Possible applications concern the radiation field generated by Josephson tunnelling in thick SNS junctions in YBCO and by current flow in molecular nano-devices.

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First-principles calculation of current density in molecular devices

Cited by 20 publications

References 40 publications

Time-dependent quantum transport: An efficient method based on Liouville-von-Neumann equation for single-electron density matrix

Time-dependent quantum transport: An efficient method based on Liouville-von-Neumann equation for single-electron density matrix

First-principles investigation of alternating current density distribution in molecular devices

High-Frequency Electromagnetic Emission from Non-Local Wavefunctions

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