Imperial College London
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ProfessorAronWalsh

Faculty of Engineering, Department of Materials

Chair in Materials Design
 
 
 
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Contact

 

+44 (0)20 7594 1178a.walsh Website

 
 
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Location

 

2.10Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@inproceedings{Silva:2020:10.1016/j.matpr.2019.10.057,
author = {Silva, EL and Santos, MC and Skelton, JM and Yang, T and Santos, T and Parker, SC and Walsh, A},
doi = {10.1016/j.matpr.2019.10.057},
pages = {373--382},
title = {Electronic and Phonon Instabilities in Bilayer Graphene under Applied External Bias},
url = {http://dx.doi.org/10.1016/j.matpr.2019.10.057},
year = {2020}
}
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RIS format (EndNote, RefMan)

TY  - CPAPER
AB  - We have performed electronic-structure and lattice-dynamics calculations on the AB and AA structures of bilayer graphene. We study the effect of external electric fields and compare results obtained with different levels of theory to existing theoretical and experimental results. Application of an external field to the AB bilayer alters the electronic spectrum, with the bands changing under bias from a parabolic to a "Mexican hat" structure. This results in a semi-metal-To-semiconductor phase transition, with the size of the induced electronic band-gap being tuneable through the field strength. A reduction of continuous symmetry from a hexagonal to a triangular lattice is also evidenced through in-plane electronic charge inhomogeneities between the sublattices. When spin-orbit coupling is turned on for the AB system, we find that the bulk gap decreases, gradually increasing for larger intensities of the bias. Under large bias the energy dispersion recovers the Mexican hat structure, since the energy interaction between the layers balances the coupling interaction. We find that external bias perturbs the harmonic phonon spectra and leads to anomalous behaviour of the out-of-plane flexural ZA and layer-breathing ZO' modes. For the AA system, the electronic and phonon dispersions both remain stable under bias, but the phonon spectrum exhibits zone-center imaginary modes due to layersliding dynamical instabilities.
AU  - Silva,EL
AU  - Santos,MC
AU  - Skelton,JM
AU  - Yang,T
AU  - Santos,T
AU  - Parker,SC
AU  - Walsh,A
DO  - 10.1016/j.matpr.2019.10.057
EP  - 382
PY  - 2020///
SP  - 373
TI  - Electronic and Phonon Instabilities in Bilayer Graphene under Applied External Bias
UR  - http://dx.doi.org/10.1016/j.matpr.2019.10.057
ER  -
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