A review of modeling interacting transient phenomena with non-equilibrium Green functions

Hirsbrunner, Mark R.; Philip, Timothy M.; Basa, Bora; Kim, Young-Seok; Park, Moon Jip; Gilbert, Matthew J.

doi:10.1088/1361-6633/aafe5f

Cited by 27 publications

(20 citation statements)

References 169 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, a nonzero Γ arises from the coupling to phonons by treating the interaction within the first Born approximation. For the calculation of Green's function, this approximation gives a result semiquantitatively consistent with the more accurate self-consistent methods for weak electron-phonon interactions (32).…”

Section: Resultsmentioning

confidence: 53%

Theory of bulk photovoltaic effect in Anderson insulator

Ishizuka

Nagaosa

2021

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The localization of wavefunction by disorder makes a conductive material an insulator with vanishing conductivity at zero temperature. A similar outcome is expected for the photocurrent in semiconductor p-n junctions because the photoexcited carriers cannot drift through the device. In contrast, we here show numerically that the bulk photovoltaic effect—the photovoltaic effect in noncentrosymmetric bulk materials—occurs in a noncentrosymmetric, disordered, one-dimensional insulator where all eigenstates are localized. We find this photocurrent remains, even when the energy scale of random potential is larger than the bandwidth. On the other hand, the photocurrent decays exponentially when the excitation is local, i.e., when only a part of the device is illuminated. The photocurrent also vanishes if the relaxation occurs only by contact with the electrodes. Our result implies that the ratio of the photovoltaic current and the direct current by the variable-range hopping increases with decreasing temperature. These results suggest a route to design high-efficiency solar cells and photodetectors.

show abstract

Section: Resultsmentioning

confidence: 53%

Theory of bulk photovoltaic effect in Anderson insulator

Ishizuka

Nagaosa

2021

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…It is computationally very challenging to model transient quantum heat transport by phonon NEGF formalism due to the memory effect in temporal integration of Green's function and self-energy. There has been much progress in electron NEGF for modeling transient phenomena, such as the generalized Kadanoff-Baym ansatz framework [74]. It is a good strategy to borrow the techniques from the transient electron NEGF, which are well summarized in a very recent review [74].…”

Section: Third-order Term In Hamiltonianmentioning

confidence: 99%

“…There has been much progress in electron NEGF for modeling transient phenomena, such as the generalized Kadanoff-Baym ansatz framework [74]. It is a good strategy to borrow the techniques from the transient electron NEGF, which are well summarized in a very recent review [74].…”

Section: Third-order Term In Hamiltonianmentioning

confidence: 99%

Quantum mechanical modeling of anharmonic phonon-phonon scattering in nanostructures

et al. 2020

View full text Add to dashboard Cite

The coherent quantum effect has become increasingly important in the heat dissipation bottleneck of semiconductor nanoelectronics with the characteristic size recently shrinking down to a few nanometers scale. However, the quantum mechanical model remains elusive for anharmonic phonon-phonon scattering in extremely small nanostructures with broken translational symmetry. It is a long-term challenging task to correctly simulate quantum heat transport including anharmonic scattering at a scale relevant to practical applications. In this article, we present a clarified theoretical formulation of anharmonic phonon nonequilibrium Green's function (NEGF) formalism for both one-and three-dimensional nanostructures, through a diagrammatic perturbation expansion and an introduction of Fourier's representation to both harmonic and anharmonic terms. A parallelized computational framework with first-principle force constants input is developed for large-scale quantum heat transport simulation. Some crucial approximations in numerical implementation are investigated to ensure the balance between numerical accuracy and efficiency. A quantitative validation is demonstrated for the anharmonic phonon NEGF formalism and computational framework by modeling cross-plane heat transport through a silicon thin film. The phonon-phonon scattering is shown to appreciably enhance the thermal resistance or conductance in extremely small homogeneous or heterogeneous thin films. The present methodology provides a robust platform for the device quantum thermal modeling, as well as a study on the transition from coherent to incoherent heat transport in nanophononic crystals. This work thus paves the way to understand and to manipulate heat conduction via the wave nature of phonons.

show abstract

“…] † } is the broadening function for the left (right) electrode, and Σ L(R) is the contact self-energy for the left (right) electrode [28][29][30]. The retarded Green function is given as…”

Section: Device Simulationsmentioning

confidence: 99%

First-Principles Evaluation of fcc Ruthenium for its use in Advanced Interconnects

Philip¹,

Lanzillo²,

Gunst

et al. 2020

Phys. Rev. Applied

Self Cite

View full text Add to dashboard Cite

As the semiconductor industry turns to alternate conductors to replace Cu for future interconnect nodes, much attention has been focused on evaluating the electrical performance of Ru. The typical hexagonal close-packed (hcp) phase has been extensively studied, but relatively little attention has been paid to the face-centered cubic (fcc) phase, which has been shown to nucleate in confined structures and may be present in tight-pitch interconnects. Using ab initio techniques, we benchmark the performance of fcc Ru. We find that the phonon-limited bulk resistivity of the fcc Ru is less than half of that of hcp Ru, a feature we trace back to the stronger electron-phonon coupling elements in hcp Ru that are geometrically inherited from the modified Fermi surface shape of the fcc crystal. Despite this benefit of the fcc phase, high grain boundary scattering results in increased resistivity compared to Cu-based interconnects with similar average grain size. We find, however, that the line resistance of fcc Ru is lower than that of Cu below 21 nm line width due to the conductor volume lost to adhesion and wetting liners. In addition to studying bulk transport properties, we evaluate the performance of adhesion liners for fcc Ru. We find that it is energetically more favorable for fcc Ru to bind directly to silicon dioxide than through conventional adhesion liners such as TaN and TiN. In the case that a thin liner is necessary for the Ru deposition technique, we find that the vertical resistance penalty of a liner for fcc Ru can be up to eight times lower than that calculated for conventional liners used for Cu interconnects. Our calculations, therefore, suggest that the formation of the fcc phase of Ru may be a beneficial for advanced, low-resistance interconnects. arXiv:2001.02216v3 [cond-mat.mtrl-sci] a) fcc b) hcp

show abstract

A review of modeling interacting transient phenomena with non-equilibrium Green functions

Cited by 27 publications

References 169 publications

Theory of bulk photovoltaic effect in Anderson insulator

Theory of bulk photovoltaic effect in Anderson insulator

Quantum mechanical modeling of anharmonic phonon-phonon scattering in nanostructures

First-Principles Evaluation of fcc Ruthenium for its use in Advanced Interconnects

Contact Info

Product

Resources

About