Ab initio phonon self-energies and fluctuation diagnostics of phonon anomalies: Lattice instabilities from Dirac pseudospin physics in transition metal dichalcogenides
Abstract
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 1 H -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 1 H -TaS2 and similar transition metal dichalcogenides.
- Publication:
-
Physical Review B
- Pub Date:
- April 2020
- DOI:
- 10.1103/PhysRevB.101.155107
- arXiv:
- arXiv:1911.02450
- Bibcode:
- 2020PhRvB.101o5107B
- Keywords:
-
- Condensed Matter - Strongly Correlated Electrons;
- Condensed Matter - Mesoscale and Nanoscale Physics;
- Condensed Matter - Materials Science
- E-Print:
- Revised manuscript with ancillary scripts and data, 15 pages, 9 figures