Nonadiabatic phonon spectra and their implications in various materials – Nina Girotto Erhardt

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Nonadiabatic phonon spectra and their implications in various materials

Nina Girotto Erhardt
Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Belgium
Email: nina.girotto@uclouvain.be

The talk will only be broadcast via Zoom:

https://hu-berlin.zoom-x.de/j/63217651382?pwd=1satvcVjx4fLfnCjKlkdLBj8eowKLP.1

Abstract:

We will delve into the role of dynamical electron-phonon coupling and provide an overview of the consequences the nonadiabatic effects have on material properties. Using examples of several bulk and two-dimensional materials, we will show how the nonadiabatic effects appear in their phonon spectra and renormalize superconducting temperature prediction, total electron-phonon coupling strength, temperature dependence of electron scattering rate, and help us understand phase diagrams. We will then tackle some cases in which we need to go beyond the first-order dynamical electron-phonon coupling. For MgB₂, higher-orders of electron-phonon coupling affect its whole phonon spectrum, especially its temperature-dependence. The real strength of these higher-order, or electron-mediated anharmonic effects, lies in their ability to capture large broadening contributions for longwavelength phonons, crucial to explain temperature-dependent Raman spectra in graphene. Further, they also renormalize the temperature of soft-mode instability in TiSe₂ and doped MoS₂, improving our understanding of electron-phonon fluctuations in charge-density wave materials.