A Theory for Colors of Strongly Correlated Electronic Systems: Article No. 5565

Swagata Acharya, Dimitar Pashov, Cedric Weber, Mark van Schilfgaarde, Alexander Lichtenstein, Mikhail Katsnelson

Research output: Contribution to journalArticlepeer-review

2 Scopus Citations

Abstract

Many strongly correlated transition metal insulators are colored, even though they have band gaps much larger than the highest energy photons from the visible light. An adequate explanation for the color requires a theoretical approach able to compute subgap excitons in periodic crystals, reliably and without free parameters - a formidable challenge. The literature often fails to disentangle two important factors: what makes excitons form and what makes them optically bright. We pick two archetypal cases as examples: NiO with green color and MnF2 with pink color, and employ two kinds of ab initio many body Green's function theories; the first, a perturbative theory based on low-order extensions of the GW approximation, is able to explain the color in NiO, while the same theory is unable to explain why MnF2 is pink. We show its color originates from higher order spin-flip transitions that modify the optical response, which is contained in dynamical mean-field theory (DMFT). We show that symmetry lowering mechanisms may determine how 'bright' these excitons are, but they are not fundamental to their existence.
Original languageAmerican English
Number of pages10
JournalNature Communications
Volume14
DOIs
StatePublished - 2023

Bibliographical note

See NREL/JA-5F00-82782 for paper as published in arXiv

NREL Publication Number

  • NREL/JA-5F00-87579

Keywords

  • Green's function
  • many-body theory
  • MnF2 with pink color
  • NiO with green color
  • perturbative theory
  • quasi-particle excitations
  • spin-flip transitions
  • transition metal insulators

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