Dresden 2020 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 27: 2D semiconductors and van der Waals heterostructures III (joint session HL/DS)

HL 27.5: Vortrag

Dienstag, 17. März 2020, 11:15–11:30, POT 81

Broken adiabaticity induced by Lifshitz transition in MoS₂ and WS₂ single layers — •Dino Novko — Institute of Physics, Zagreb, Croatia — Donostia International Physics Center (DIPC), San Sebastián, Spain

The breakdown of the adiabatic Born-Oppenheimer approximation is striking dynamical phenomenon, however, it occurs only in a handful of layered materials. Here I show that adiabaticity breaks down in doped single-layer transition metal dichalcogenides in a quite intriguing manner. Namely, significant nonadiabatic coupling, which acts on frequencies of the Raman-active modes, is prompted by a Lifshitz transition due to depopulation and population of multiple valence and conduction valleys, respectively. The outset of the latter event is shown to be dictated by the interplay of highly non-local electron-electron interaction and spin-orbit coupling. In addition, intense electron-hole pair scatterings due to electron-phonon coupling are inducing phonon linewidth modifications as a function of doping. Comprehending these intricate dynamical effects turns out to be a key for mastering characterization of electron doping in two-dimensional nano-devices by means of Raman spectroscopy.