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Photoemission Spectra from the Extended Koopman's Theorem, Revisited.

S Di Sabatino1,2,3, J Koskelo2,3, J Prodhon2

  • 1Laboratoire de Chimie et Physique Quantiques, Université de Toulouse, CNRS, UPS, Toulouse, France.

Frontiers in Chemistry
|October 25, 2021
PubMed
Summary
This summary is machine-generated.

The Extended Koopman's Theorem (EKT) links with many-body effective energy theory (MEET) for calculating charged excitations and spectral functions. This connection enhances both theories, enabling EKT to compute full spectral functions and MEET to use optimal basis sets.

Keywords:
QMCRDMFTextended Koopman’s theoremone-body Green’s functionphotoemissionstrong correlation

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Area of Science:

  • Computational Chemistry
  • Quantum Mechanics
  • Materials Science

Background:

  • The Extended Koopman's Theorem (EKT) offers a method for computing charged excitations.
  • The many-body effective energy theory (MEET) was developed to calculate spectral functions, relevant to photoemission spectroscopy.

Purpose of the Study:

  • To establish a theoretical link between EKT and MEET.
  • To demonstrate how this link can improve calculations of charged excitations and spectral functions.
  • To illustrate the practical application of the combined approach.

Main Methods:

  • Connecting the diagonal approximation of EKT with MEET removal and addition energies.
  • Extending EKT to compute the full spectral function.
  • Utilizing EKT to determine optimal basis sets for MEET.

Main Results:

  • The lowest level of MEET approximation directly corresponds to the diagonal approximation of EKT.
  • EKT can be extended to calculate the complete spectral function.
  • Solving the EKT secular equation provides an optimal basis set for MEET.

Conclusions:

  • A significant theoretical bridge between EKT and MEET has been established.
  • This integration offers mutual benefits, enhancing the predictive power of both theoretical frameworks.
  • The combined approach was successfully demonstrated on the Hubbard dimer and bulk silicon systems.