Abstract
Twisting bilayer sheets of graphene have been proven to be an efficient way to manipulate the electronic Dirac-like properties, resulting in flat bands at magic angles. Inspired by the electronic model, we develop a continuum model for the lattice dynamics of twisted bilayer graphene and we show that a remarkable band flattening applies to almost all the high-frequency in-plane lattice vibration modes, including the valley Dirac phonon, valley optical phonon, and zone-center optical phonon bands. Utilizing an approximate approach, we estimate small but finite magic angles at which a vanishing phonon bandwidth is expected. In contrast to the electronic case, the existence of a restoring potential prohibits the emergence of a magic angle in a more accurate modeling. The predicted phonon band flattening is highly tunable by the twist angle and this strong dependence is directly accessible by spectroscopic tools.
| Original language | English |
|---|---|
| Article number | 125401 |
| Journal | Physical Review B |
| Volume | 108 |
| Issue number | 12 |
| Early online date | 15 Sept 2023 |
| DOIs | |
| Publication status | Published - 15 Sept 2023 |
Bibliographical note
Funding Information:The authors thank T. Cea and H. Ochoa for useful discussions. IMDEA Nanociencia acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (Grant No. CEX2020-001039-S/AEI/10.13039/501100011033). F.G. acknowledges funding from the European Commission, within the Graphene Flagship, Core 3, Grant No. 881603, and from Grants No. NMAT2D (Comunidad de Madrid, Spain) and No. SprQuMat (Ministerio de Ciencia e Innovación, Spain), and financial support through the (MAD2D-CM)-MRR MATERIALES AVANZADOS-IMDEA-NC. E.C. acknowledges financial support from PNRR MUR Project No. PE0000023-NQSTI. H.R. acknowledges the support from the Swedish Research Council (VR Starting Grant No. 2018-04252).
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics