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Underlying Topological Dirac Nodal Line Mechanism of the Anomalously Large Electron-Phonon Coupling Strength on a Be (0001) Surface

Ronghan Li, Jiangxu Li, Lei Wang, Jiaxi Liu, Hui Ma, Hai-Feng Song, Dianzhong Li, Yiyi Li, and Xing-Qiu Chen
Phys. Rev. Lett. 123, 136802 – Published 23 September 2019
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Abstract

Beryllium has recently been discovered to harbor a Dirac nodal line (DNL) in its bulk phase and the DNL-induced nontrivial surface states (DNSSs) on its (0001) surface, rationalizing several already-existing historic puzzles [Phys. Rev. Lett. 117, 096401 (2016)]. However, to date the underlying mechanism as to why its (0001) surface exhibits an anomalously large electron-phonon coupling effect (λephs1.0) remains unresolved. Here, by means of first-principles calculations, we show that the coupling of the DNSSs with the phononic states mainly contributes to its novel surface e-ph enhancement. Besides the fact that the experimentally observed λephs and the main Eliashberg coupling function (ECF) peaks are reproduced well in our current calculations, we decompose the ECF α2F(k,q;v) and the e-ph coupling strength λ(k,q;v) as a function of each electron momentum (k), each phonon momentum (q), and each phonon mode (v), evidencing the robust connection between the DNSSs and both α2F(k,q;v) and λ(k,q;v). The results reveal the strong e-ph coupling between the DNSSs and the phonon modes, which contributes over 80% of the λephs coefficient on the Be (0001) surface. It highlights that the anomalously large e-ph coefficient on the Be (0001) surface can be attributed to the presence of its DNL-induced DNSSs, clarifying the long-debated mechanism.

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  • Received 20 December 2018
  • Revised 8 August 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.136802

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ronghan Li1,2,†, Jiangxu Li1,2,†, Lei Wang1,2, Jiaxi Liu1,2, Hui Ma1, Hai-Feng Song3, Dianzhong Li1,2, Yiyi Li1,2, and Xing-Qiu Chen1,2,*

  • 1Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 110016 Shenyang, Liaoning, People’s Republic of China
  • 2School of Materials Science and Engineering, University of Science and Technology of China, Heifei 230026, People’s Republic of China
  • 3Institute of Applied Physics and Computational Mathematics, Beijing 100094, People’s Republic of China

  • *Corresponding author. xingqiu.chen@imr.ac.cn
  • These authors contributed equally to this work.

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Issue

Vol. 123, Iss. 13 — 27 September 2019

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