Comment on “Electron-phonon coupling in two-dimensional silicene and germanene”

Comment on “Electron-phonon coupling in two-dimensional silicene and germanene” In their work, Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] employing density functional perturbation theory (DFPT) calculations, demonstrate that silicene and germanene show weaker Kohn anomalies in the Γ-Eg and K-A1 phonon modes, compared to graphene. Furthermore, the electron-phonon (e-ph) coupling matrix elements were computed using the frozen-phonon approach. They found that in silicene the average e-ph coupling matrix element square over the Fermi-surface ⟨gqν2⟩F is about 50% of those in graphene, but in germanene is weaker and nearly negligible. However, Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] argue that the smaller Fermi velocity in silicene compensates the reduced ⟨gqν2⟩F, leading to phonon linewidths (γqν) slightly larger than those in graphene. In this Comment, we show that the DFPT and the frozen-phonon results of Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] for silicene are inconsistent. Additionally, we have evaluated the e-ph coupling using direct DFPT calculations, analytical relations, and frozen-phonon calculations, and we found systematically that ⟨gqν2⟩F and γqν in silicene are one order of magnitude smaller than in graphene, in contrast to the conclusions of Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403]. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review B American Physical Society (APS)

Comment on “Electron-phonon coupling in two-dimensional silicene and germanene”

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Comment on “Electron-phonon coupling in two-dimensional silicene and germanene”

Abstract

In their work, Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] employing density functional perturbation theory (DFPT) calculations, demonstrate that silicene and germanene show weaker Kohn anomalies in the Γ-Eg and K-A1 phonon modes, compared to graphene. Furthermore, the electron-phonon (e-ph) coupling matrix elements were computed using the frozen-phonon approach. They found that in silicene the average e-ph coupling matrix element square over the Fermi-surface ⟨gqν2⟩F is about 50% of those in graphene, but in germanene is weaker and nearly negligible. However, Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] argue that the smaller Fermi velocity in silicene compensates the reduced ⟨gqν2⟩F, leading to phonon linewidths (γqν) slightly larger than those in graphene. In this Comment, we show that the DFPT and the frozen-phonon results of Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] for silicene are inconsistent. Additionally, we have evaluated the e-ph coupling using direct DFPT calculations, analytical relations, and frozen-phonon calculations, and we found systematically that ⟨gqν2⟩F and γqν in silicene are one order of magnitude smaller than in graphene, in contrast to the conclusions of Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403].
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Publisher
The American Physical Society
Copyright
Copyright © ©2017 American Physical Society
ISSN
1098-0121
eISSN
1550-235X
D.O.I.
10.1103/PhysRevB.96.047401
Publisher site
See Article on Publisher Site

Abstract

In their work, Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] employing density functional perturbation theory (DFPT) calculations, demonstrate that silicene and germanene show weaker Kohn anomalies in the Γ-Eg and K-A1 phonon modes, compared to graphene. Furthermore, the electron-phonon (e-ph) coupling matrix elements were computed using the frozen-phonon approach. They found that in silicene the average e-ph coupling matrix element square over the Fermi-surface ⟨gqν2⟩F is about 50% of those in graphene, but in germanene is weaker and nearly negligible. However, Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] argue that the smaller Fermi velocity in silicene compensates the reduced ⟨gqν2⟩F, leading to phonon linewidths (γqν) slightly larger than those in graphene. In this Comment, we show that the DFPT and the frozen-phonon results of Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403] for silicene are inconsistent. Additionally, we have evaluated the e-ph coupling using direct DFPT calculations, analytical relations, and frozen-phonon calculations, and we found systematically that ⟨gqν2⟩F and γqν in silicene are one order of magnitude smaller than in graphene, in contrast to the conclusions of Yan et al. [Phys. Rev. B 88, 121403 (2013)PRBMDO1098-012110.1103/PhysRevB.88.121403].

Journal

Physical Review BAmerican Physical Society (APS)

Published: Jul 25, 2017

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