SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 82: Poster Session VI: Poster to Mini-Symposium: Frontiers of electronic-structure theory III
O 82.7: Poster
Mittwoch, 3. März 2021, 13:30–15:30, P
Ab initio phonon self-energies and fluctuation diagnostics of phonon anomalies: Lattice instabilities from Dirac pseudospin physics in transition metal dichalcogenides — •Jan Berges1, Erik van Loon1, Arne Schobert1, Malte Rösner2, and Tim Wehling1 — 1Universität Bremen, Germany — 2Radboud Universiteit Nijmegen, The Netherlands
We present an ab initio approach for the calculation of phonon self-energies and their fluctuation diagnostics, which allows us to identify the electronic processes behind phonon anomalies. Application to the transition-metal-dichalcogenide monolayer TaS2 reveals that coupling between the longitudinal–acoustic phonons and the electrons from an isolated low-energy metallic band is entirely responsible for phonon anomalies such as the mode softening and associated charge-density waves observed in this material. Our analysis allows us to distinguish between different mode-softening mechanisms including matrix-element effects, Fermi-surface nesting, and Van Hove scenarios. We find that matrix-element effects originating from a peculiar type of Dirac pseudospin textures control the charge-density-wave physics in TaS2 and similar transition metal dichalcogenides.