Phonon self-energy corrections: To screen, or not to screen

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<oai_dc:dc xmlns:dc="" xmlns:oai_dc="" xmlns:xsi="" xsi:schemaLocation="">
  <dc:creator>Berges, Jan</dc:creator>
  <dc:creator>Girotto, Nina</dc:creator>
  <dc:creator>Wehling, Tim</dc:creator>
  <dc:creator>Marzari, Nicola</dc:creator>
  <dc:creator>Poncé, Samuel</dc:creator>
  <dc:description>First-principles calculations of phonons are often based on the adiabatic approximation and on Brillouin-zone samplings that might not always be sufficient to capture the subtleties of Kohn anomalies. These shortcomings can be addressed through corrections to the phonon self-energy arising from the low-energy electrons. The exact self-energy involves a product of a bare and a screened electron-phonon vertex [Rev. Mod. Phys. 89, 015003 (2017)]; still, calculations often employ two adiabatically screened vertices, which have been proposed as a reliable approximation for self-energy differences [Phys. Rev. B 82, 165111 (2010)]. We assess the accuracy of both approaches in estimating the phonon spectral functions of model Hamiltonians and the adiabatic low-temperature phonon dispersions of monolayer TaS₂ and doped MoS₂. We find that the approximate method yields excellent corrections at low computational cost, due to its designed error cancellation to first order, while using a bare vertex could in principle improve these results but is challenging in practice. We offer an alternative strategy based on downfolding to partially screened phonons and interactions [Phys. Rev. B 92, 245108 (2015)]. This is a natural scheme to include electron-electron interactions and tackle phonons in strongly correlated materials and the frequency dependence of the electron-phonon vertex.

This record contains (i) a patch for the PHonon and EPW codes of Quantum ESPRESSO, (ii) the Python scripts and data necessary to create all figures shown in our paper, (iii) a minimal working example of the optimization of quadrupole tensors, and (iv) the Quantum ESPRESSO input files we have used.</dc:description>
  <dc:publisher>Materials Cloud</dc:publisher>
  <dc:rights>GNU General Public License v2.0 or later</dc:rights>
  <dc:subject>electron-phonon coupling</dc:subject>
  <dc:subject>first principles</dc:subject>
  <dc:subject>2D materials</dc:subject>
  <dc:title>Phonon self-energy corrections: To screen, or not to screen</dc:title>