Dynamical reconstruction of the exciton in LiF with inelastic x-ray scattering

Abbamonte, Peter; Graber, Tim; Reed, J.; Smadici, S.; Yeh, Chih-Hung; Shukla, Abhay; Rueff, Jean‐Pascal; Ku, Wei

doi:10.1073/pnas.0801623105

Cited by 50 publications

(60 citation statements)

References 27 publications

(31 reference statements)

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“…In the case of a prototypical wide-gap insulator such as lithium fluoride, the dynamic structure factor S(q,ω) was obtained in excellent agreement with accurate NRIXS data [18]. However, in contrast to LiF, in hexagonal boron nitride (h-BN), a layered material that is the insulating counterpart of graphite, a recent comparison [19] between BSE calculations and NRIXS data revealed a mismatch at high momentum transfers.…”

Section: Introductionmentioning

confidence: 71%

Exciton energy-momentum map of hexagonal boron nitride

et al. 2015

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Understanding and controlling the way excitons propagate in solids is a key for tailoring materials with improved optoelectronic properties. A fundamental step in this direction is the determination of the exciton energy-momentum dispersion. Here, thanks to the solution of the parameter-free Bethe-Salpeter equation (BSE), we draw and explain the exciton energy-momentum map of hexagonal boron nitride (h-BN) in the first three Brillouin zones. We show that h-BN displays strong excitonic effects not only in the optical spectra at vanishing momentum q, as previously reported, but also at large q. We validate our theoretical predictions by assessing the calculated exciton map by means of an inelastic x-ray scattering (IXS) experiment. Moreover, we solve the discrepancies between previous experimental data and calculations, proving then that the BSE is highly accurate through the whole momentum range. Therefore, these results put forward the combination BSE and IXS as the tool of choice for addressing the exciton dynamics in complex materials.

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Section: Introductionmentioning

confidence: 71%

Exciton energy-momentum map of hexagonal boron nitride

et al. 2015

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“…This also implies that the necessary condition for simplified models to properly describe the exciton dispersion in LiF is to take into account (implicitly or explicitly) the electronic band dispersion. 4,32,33 It is interesting to compare also the triplet with the singlet, in order to directly evaluate the e-h exchange term, which has the effect of tempering the exciton dispersion, which otherwise would become too big. The final bandwidth of the exciton is 0.67 eV.…”

Section: Lithium Fluoridementioning

confidence: 99%

Exciton dispersion from first principles

Gatti

Sottile

2013

Phys. Rev. B

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We present a scheme to calculate exciton dispersions in real materials that is based on the first-principles many-body Bethe-Salpeter equation. We assess its high level of accuracy by comparing our results for LiF with recent inelastic x-ray scattering experimental data on a wide range of energy and momentum transfer. We show its great analysis power by investigating the role of the different electron-hole interactions that determine the exciton band structure and the peculiar "exciton revival" at large momentum transfer. Our calculations for solid argon are a prediction and a suggestion for future experiments. These results demonstrate that the first-principles Bethe-Salpeter equation is able to describe the dispersion of localized and delocalized excitons on equal footing and represent a key step for the ab initio study of the exciton mobility.

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“…These N-t 2g are the ones being integrated out to derive the effective d 4 picture. Note that this change of perspective is the same as that employed in the construction of the well-known Zhang-Rice singlet in the cuprate high-temperature superconductors [59,60], and the same concept has been applied to the study of local excitations in correlated NiO [58,61] and LiF [62,63]. The above effective d 4 picture, while ideal to study the Jahn-Teller instability and other local properties like the local magnetic moment and local excitations, is not suitable for studying long-range properties.…”

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confidence: 99%

What is the Valence of Mn inGa1−xMnxN?

et al. 2015

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We investigate the current debate on the Mn valence in Ga1−xMnxN, a diluted magnetic semiconductor (DMSs) with a potentially high Curie temperature. From a first-principles Wannier-function analysis, we unambiguously find the Mn valence to be close to 2+ (d 5 ), but in a mixed spin configuration with average magnetic moments of 4µB. By integrating out high-energy degrees of freedom differently, we further derive for the first time from first-principles two low-energy pictures that reflect the intrinsic dual nature of the doped holes in the DMS: 1) an effective d 4 picture ideal for local physics, and 2) an effective d 5 picture suitable for extended properties. In the latter, our results further reveal a few novel physical effects, and pave the way for future realistic studies of magnetism. Our study not only resolves one of the outstanding key controversies of the field, but also exemplifies the general need for multiple effective descriptions to account for the rich low-energy physics in many-body systems in general.

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Dynamical reconstruction of the exciton in LiF with inelastic x-ray scattering

Cited by 50 publications

References 27 publications

Exciton energy-momentum map of hexagonal boron nitride

Exciton energy-momentum map of hexagonal boron nitride

Exciton dispersion from first principles

What is the Valence of Mn inGa1−xMnxN?

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