CSMB Colloquium@T²P
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Center for the Science of Materials Berlin (CSMB)
Nonadiabatic phonon spectra and their implications in various materials
Nina Girotto Erhardt
Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Belgium
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.
The talk will only be broadcast via Zoom.