Acoustic magnons in the long-wavelength limit: Investigating the Goldstone violation in many-body perturbation theory

Müller, Mathias C. T. D.; Friedrich, Christoph; Blügel, Stefan

doi:10.1103/physrevb.94.064433

Cited by 39 publications

(48 citation statements)

References 58 publications

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“…As with Dyson's equation, equations with the Bethe-Salpeter form appear in different contexts in many-body theory. For example, a Bethe-Salpeter equation can also describe spin-flip excitations in magnetic materials (Müller et al, 2016).…”

Section: Current Challenges and Beyond Gwmentioning

confidence: 99%

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

2019

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The GW approximation in electronic structure theory has become a widespread tool for predicting electronic excitations in chemical compounds and materials. In the realm of theoretical spectroscopy, the GW method provides access to charged excitations as measured in direct or inverse photoemission spectroscopy. The number of GW calculations in the past two decades has exploded with increased computing power and modern codes. The success of GW can be attributed to many factors: favorable scaling with respect to system size, a formal interpretation for charged excitation energies, the importance of dynamical screening in real systems, and its practical combination with other theories. In this review, we provide an overview of these formal and practical considerations. We expand, in detail, on the choices presented to the scientist performing GW calculations for the first time. We also give an introduction to the many-body theory behind GW , a review of modern applications like molecules and surfaces, and a perspective on methods which go beyond conventional GW calculations. This review addresses chemists, physicists and material scientists with an interest in theoretical spectroscopy. It is intended for newcomers to GW calculations but can also serve as an alternative perspective for experts and an up-to-date source of computational techniques.

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Section: Current Challenges and Beyond Gwmentioning

confidence: 99%

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

2019

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“…For an analysis of BSE applied to the magnon channel, see, for example, Ref. [30]. Instead, the total spin is not yet a good quantum number, and the origin of this can be traced back to the fact that |φ nk↑ (x)| 2 = |φ nk↓ (x)| 2 .…”

Section: The Magnetic Casementioning

confidence: 99%

Spinorial formulation of the GW -BSE equations and spin properties of excitons in two-dimensional transition metal dichalcogenides

et al. 2021

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In many paradigmatic materials, such as transition metal dichalcogenides, the role played by the spin degrees of freedom is as important as the one played by the electron-electron interaction. Thus an accurate treatment of the two effects and of their interaction is necessary for an accurate and predictive study of the optical and electronic properties of these materials. Despite the fact that the GW-BSE approach correctly accounts for electronic correlations, the spin-orbit coupling effect is often neglected or treated perturbatively. Recently, spinorial formulations of GW-BSE have become available in different flavors in material-science codes. However, an accurate validation and comparison of different approaches is still missing. In this work, we go through the derivation of the noncollinear GW-BSE approach. The scheme is applied to transition metal dichalcogenides comparing the perturbative and full spinorial approaches. Our calculations reveal that dark-bright exciton splittings are generally improved when the spin-orbit coupling is included nonperturbatively. The exchange-driven intravalley mixing between the A and B excitons is found to play a role for Mo-based systems, being especially strong in the case of MoSe 2 . We finally compute the excitonic spin and use it to sharply analyze the spinorial properties of transition metal dichalcogenide excitonic states.

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“…(1) many-body perturbation theory where the susceptibility is obtained by solving a Bethe-Salpeter equation [13][14][15][16][17][18] and (2) time-dependent density functional theory (TDDFT) [19][20][21], which (although exact in principle) is limited by approximations for the applied exchange-correlation kernel. Both of these methods are restricted to T = 0 and thermodynamical properties are currently inaccessible by direct ab initio methods.…”

Section: Introductionmentioning

confidence: 99%

Dynamic transverse magnetic susceptibility in the projector augmented-wave method: Application to Fe, Ni, and Co

Skovhus

Olsen

2021

Phys. Rev. B

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We present a first principles implementation of the dynamic transverse magnetic susceptibility in the framework of linear response time-dependent density functional theory. The dynamic susceptibility allows one to obtain the magnon dispersion as well as magnon lifetimes for a particular material, which strongly facilitates the interpretation of inelastic neutron scattering experiments as well as other spectroscopic techniques. We apply the method to Fe, Ni, and Co and perform a thorough convergence analysis with respect to the basis set size, k-point sampling, spectral smearing, and unoccupied bands. In particular, it is shown that while the gap error (acoustic magnon energy at q = 0) is highly challenging to converge, the spin-wave stiffness and the dispersion relation itself are much less sensitive to convergence parameters. Our final results agree well with experimentally extracted magnon dispersion relations except for Ni, where it is well known that the exchange splitting energy is poorly represented in the local density approximation. We also find good agreement with previous first principles calculations and explain how differences in the calculated dispersion relations can arise from subtle differences in computational approaches.

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Acoustic magnons in the long-wavelength limit: Investigating the Goldstone violation in many-body perturbation theory

Cited by 39 publications

References 58 publications

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

Spinorial formulation of the GW -BSE equations and spin properties of excitons in two-dimensional transition metal dichalcogenides

Dynamic transverse magnetic susceptibility in the projector augmented-wave method: Application to Fe, Ni, and Co

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