Electron–plasmon and electron–magnon scattering in ferromagnets from first principles by combining GW and GT self-energies

Nabok, Dmitrii; Blügel, Stefan; Friedrich, Christoph

doi:10.1038/s41524-021-00649-8

Cited by 16 publications

(22 citation statements)

References 53 publications

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“…1 contains 2body terms, which cannot be reduced to a single propagator interacting with itself through a screened potential W . The leading order terms in Σ from Γ W are identical to the direct terms found in the screened T-matrix expansion [16,38,39]. The higher order screened T-matrix is outside of the imposed truncation and results from the second type of closure (resummation restricted to a selected type of diagrams) discussed below.…”

mentioning

confidence: 75%

“…Using this closure, we generated a self-energy expression containing (lowest order) direct and exchange T-matrix terms for both pp and ph channels. In contrast, such diagrams were previously generated by imposing an Ansatz for the two-body interactions and typically only one of the channels, pp or ph, was applied [16,38,39]. Our derivation shows that both need to be added simultaneously and at equal footing.…”

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confidence: 97%

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Self-consistency in $GWΓ$ formalism leading to quasiparticle-quasiparticle couplings

Mejuto-Zaera¹,

Vlček²

2022

Preprint

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Within many-body perturbation theory, Hedin's formalism offers a systematic way to iteratively compute the self-energy Σ of any interacting system, provided one can evaluate the interaction vertex Γ exactly. This is however impossible in general, for it involves the functional derivative of Σ with respect to the Green's function. Here, we analyze the structure of this derivative, splitting it into four contributions and outlining the type of quasiparticle interactions that each of them generate. Moreover we show how, in the implementation of self-consistency, the action of these contributions can be classified into two: a quantitative renormalization of previously included interaction terms, and the inclusion of qualitatively novel interaction terms through successive functional derivatives of Γ itself, neglected until now. Implementing this latter type of self-consistency can extend the validity of Hedin's equations towards the high interaction limit, as we show in the example of the Hubbard dimer. Our analysis also provides a unifying perspective on the perturbation theory landscape, showing how the T-matrix approach is completely contained in Hedin's formalism.

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confidence: 75%

mentioning

confidence: 97%

Self-consistency in $GWΓ$ formalism leading to quasiparticle-quasiparticle couplings

Mejuto-Zaera¹,

Vlček²

2022

Preprint

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“…6 This coupled dynamics of an electron-bosonic composite system is often initiated by the excitation with an electromagnetic field, and complexity can further increase if the quantum nature of the electromagnetic field and its bosonic excitations are taken into account explicitly. [7][8][9][10][11][12] Bosonic excitations naturally emerge in condensed matter, e.g., plasmons, 13 phonons, [14][15][16] or magnons. 13 Here, such excitations can couple to electrons and influence the electronic properties.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9][10][11][12] Bosonic excitations naturally emerge in condensed matter, e.g., plasmons, 13 phonons, [14][15][16] or magnons. 13 Here, such excitations can couple to electrons and influence the electronic properties. For example, exciton-phonon coupling [17][18][19][20][21][22] in semiconductors affects exciton mobilities, the phononbottleneck mechanism reduces energy loss of hot carriers, [23][24][25][26][27] and phonon-magnon scattering 28,29 induced by electronphonon coupling can lead to ultrafast demagnetization, 30 to mention a few examples.…”

Section: Introductionmentioning

confidence: 99%

Real-time non-adiabatic dynamics in the one-dimensional Holstein model: Trajectory-based vs exact methods

Brink,

Gräber,

Hopjan

et al. 2022

Preprint

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We benchmark a set of quantum-chemistry methods including the multitrajectory Ehrenfest, the fewest-switches surface-hopping, and the multiconfigurational Ehrenfest method against exact quantum-many-body techniques by studying real-time dynamics in the Holstein model. This is a paradigmatic model in condensed matter theory incorporating a local coupling of electrons to Einstein phonons. For the two-site and three-site Holstein model, we discuss the exact and quantum-chemistry methods in terms of the Born-Huang formalism, covering different initial states, which either start on a single Born-Oppenheimer surface, or with the electron localized to a single site. For extended systems with up to 51 sites, we address both the physics of single Holstein polarons and the dynamics of charge-density waves at finite electron densities. For these extended systems, we compare the quantum-chemistry methods to exact dynamics obtained from time-dependent density matrix renormalization group calculations with local basis optimization (DMRG-LBO). We observe that the multitrajectory Ehrenfest method in general only captures the ultra-short time dynamics accurately. In contrast, the surface-hopping method with suitable corrections provides a much better description of the long-time behavior, but struggles with the short-time description of coherences between different Born-Oppenheimer states. We show that the multiconfigurational Ehrenfest method yields a significant improvement over the multitrajectory Ehrenfest method and can be converged to the exact results in small systems with moderate computational efforts. We further observe that for extended systems, this convergence is slower with respect to the number of configurations. Our benchmark study demonstrates that DMRG-LBO is a useful tool for assessing the quality of the quantum-chemistry methods.

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“…Spin susceptibilities [65] may then be used to calculate electron-magnon contributions to quasiparticle energies, as in the recent work in Ref. [66]. Other codes do not seem to have this functionality implemented.…”

Section: Introductionmentioning

confidence: 99%

Fully relativistic $GW$/Bethe-Salpeter calculations in BerkeleyGW: implementation, symmetries, benchmarking, and performance

Barker,

Deslippe,

Lischner

et al. 2022

Preprint

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Computing the GW quasiparticle bandstructure and Bethe-Salpeter Equation (BSE) absorption spectra for materials with spin-orbit coupling has commonly been done by treating GW corrections and spin-orbit coupling as separate perturbations to density-functional theory. However, accurate treatment of materials with strong spin-orbit coupling (such as many topological materials of recent interest, and thermoelectrics) often requires a fully relativistic approach using spinor wavefunctions in the Kohn-Sham equation and GW /BSE. Such calculations have only recently become available, in particular for the BSE. We have implemented this approach in the plane-wave pseudopotential GW /BSE code BerkeleyGW, which is highly parallelized and widely used in the electronic-structure community. We present reference results for quasiparticle bandstructures and optical absorption spectra of solids with different strengths of spin-orbit coupling, including Si, Ge, GaAs, GaSb, CdSe, Au, and Bi 2 Se 3 . The calculated quasiparticle band gaps of these systems are found to agree with experiment to within a few tens of meV. SOC splittings are found to be generally in better agreement with experiment, including quasiparticle corrections to band energies. The absorption spectrum of GaAs is not significantly impacted by the inclusion of spin-orbit coupling due to its relatively small value (0.2 eV) in the Λ direction, while the absorption spectrum of GaSb calculated with the fully-relativistic GW -BSE captures the large spin-orbit splitting of peaks in the spectrum. For the prototypical topological insulator Bi 2 Se 3 , we find a drastic change in the low-energy bandstructure compared to that of DFT, with the fully-relativistic treatment of the GW approximation correctly capturing the parabolic nature of the valence and conduction bands after including off-diagonal self-energy matrix elements. We present the detailed methodology, approach to spatial symmetries for spinors, comparison against other codes, and performance compared to spinless GW /BSE calculations and perturbative approaches to SOC. This work aims to spur further development of spinor GW /BSE methodology in excited-state research software, and enables more accurate and detailed exploration of electronic and optical properties of materials containing elements with large atomic number.

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Electron–plasmon and electron–magnon scattering in ferromagnets from first principles by combining GW and GT self-energies

Cited by 16 publications

References 53 publications

Self-consistency in $GWΓ$ formalism leading to quasiparticle-quasiparticle couplings

Self-consistency in $GWΓ$ formalism leading to quasiparticle-quasiparticle couplings

Real-time non-adiabatic dynamics in the one-dimensional Holstein model: Trajectory-based vs exact methods

Fully relativistic $GW$/Bethe-Salpeter calculations in BerkeleyGW: implementation, symmetries, benchmarking, and performance

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