Time-dependent versus static quantum transport simulations beyond linear response

Yam, ChiYung; Zheng, Xiao; Chen, Guanhua; Wang, Y.; Frauenheim, Thomas; Niehaus, Thomas A.

doi:10.1103/physrevb.83.245448

Cited by 50 publications

(53 citation statements)

References 35 publications

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“…The effects of the leads attached to the system are represented through the corresponding self-energies. [5][6][7] This scheme has proved useful to estimate conductance in a variety of molecules and nanoscale structures coupled to semiinfinite leads. 8,9 An important limitation of these calculations is the fact that the transmission function from static DFT has resonances at the non-interacting Kohn-Sham excitation energies, which more often than not disagree with the true values.…”

Section: Introductionmentioning

confidence: 99%

Electron transport in real time from first-principles

Morzan

Ramirez

Lebrero

et al. 2017

The Journal of Chemical Physics

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While the vast majority of calculations reported on molecular conductance have been based on the static non-equilibrium Green's function formalism combined with density functional theory (DFT), in recent years a few time-dependent approaches to transport have started to emerge. Among these, the driven Liouville-von Neumann equation [C. G. Sánchez et al., J. Chem. Phys. 124, 214708 (2006)] is a simple and appealing route relying on a tunable rate parameter, which has been explored in the context of semi-empirical methods. In the present study, we adapt this formulation to a density functional theory framework and analyze its performance. In particular, it is implemented in an efficient allelectron DFT code with Gaussian basis functions, suitable for quantum-dynamics simulations of large molecular systems. At variance with the case of the tight-binding calculations reported in the literature, we find that now the initial perturbation to drive the system out of equilibrium plays a fundamental role in the stability of the electron dynamics. The equation of motion used in previous tight-binding implementations with massive electrodes has to be modified to produce a stable and unidirectional current during time propagation in time-dependent DFT simulations using much smaller leads. Moreover, we propose a procedure to get rid of the dependence of the current-voltage curves on the rate parameter. This method is employed to obtain the current-voltage characteristic of saturated and unsaturated hydrocarbons of different lengths, with very promising prospects. Published by AIP Publishing. [http://dx

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Section: Introductionmentioning

confidence: 99%

Electron transport in real time from first-principles

Morzan

Ramirez

Lebrero

et al. 2017

The Journal of Chemical Physics

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“…21 However, it has been recently found that the standard TDDFT exchange-correlation potentials do not yield any improvement over the NEGF-DFT in terms of accuracy in predicting conductance. 22 In addition to the electronic current, it is of interest to model the forces acting on the atoms under nonequilibrium conditions, i.e., under a finite bias voltage. Such forces ultimately determine the stability of current-carrying molecular devices, 23,24 but can also be exploited to deliberately control the motion of single molecules by, e.g., injecting electrons into the molecular orbitals using a scanning tunneling microscope (STM).…”

Section: Introductionmentioning

confidence: 99%

Ab initiononequilibrium quantum transport and forces with the real-space projector augmented wave method

2012

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We present an efficient implemention of a non-equilibrium Green function (NEGF) method for selfconsistent calculations of electron transport and forces in nanostructured materials. The electronic structure is described at the level of density functional theory (DFT) using the projector augmented wave method (PAW) to describe the ionic cores and an atomic orbital basis set for the valence electrons. External bias and gate voltages are treated in a self-consistent manner and the Poisson equation with appropriate boundary conditions is solved in real space. Contour integration of the Green function and parallelization over k-points and real space makes the code highly efficient and applicable to systems containing several hundreds of atoms. The method is applied to a number of different systems demonstrating the effects of bias and gate voltages, multiterminal setups, nonequilibrium forces, and spin transport.

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“…[20][21][22][23][24][25][26][27][28][29][31][32][33][34] We first solve the steady-state equations of DFT and mean-field theory to determine the parameter range for bistability. Then we go beyond the current state-of-the-art and provide a TD description of the bistability phenomenon in adiabatic TDDFT [23][24][25][26][27][28][29] and TD mean-field theory. We show how to switch between different stable states by means of ultrafast gate voltages or external biases (driving fields).…”

Section: Introductionmentioning

confidence: 99%

Correlation effects in bistability at the nanoscale: Steady state and beyond

et al. 2012

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The possibility of finding multistability in the density and current of an interacting nanoscale junction coupled to semi-infinite leads is studied at various levels of approximation. The system is driven out of equilibrium by an external bias and the nonequilibrium properties are determined by real-time propagation using both time-dependent density functional theory (TDDFT) and many-body perturbation theory (MBPT). In TDDFT the exchange-correlation effects are described within a recently proposed adiabatic local density approximation (ALDA). In MBPT the electron-electron interaction is incorporated in a many-body self-energy which is then approximated at the Hartree-Fock (HF), second-Born, and GW level. Assuming the existence of a steady state and solving directly the steady-state equations we find multiple solutions in the HF approximation and within the ALDA. In these cases we investigate whether and how these solutions can be reached through time evolution and how to reversibly switch between them. We further show that for the same cases the inclusion of dynamical correlation effects suppresses bistability.

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Time-dependent versus static quantum transport simulations beyond linear response

Cited by 50 publications

References 35 publications

Electron transport in real time from first-principles

Electron transport in real time from first-principles

Ab initiononequilibrium quantum transport and forces with the real-space projector augmented wave method

Correlation effects in bistability at the nanoscale: Steady state and beyond

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