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

2019/07/19 by Ronghan Li, Jiangxu Li, Lei Wang +7
Materials Science · Mathematics · Physics and Astronomy · #Condensed matter physics #Connection (principal bundle) #Coupling (piping) #Dirac (video compression format) #Geometry #Graphene research and applications #Lambda #Materials science #Mathematics #Phonon #Physics #Quantum and electron transport phenomena #Quantum mechanics #Surface (topology) #Topological Materials and Phenomena #cond-mat.mtrl-sci

paper · pdf · doi:10.1103/physrevlett.123.136802

published as Phys. Rev. Lett. 123, 136802 (2019) · 6 pages, 3 figures

arxiv created 2019/07/19 · openalex publication_date 2019/09/23 · arxiv updated 2019/10/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

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)PRLTAO0031-900710.1103/PhysRevLett.117.096401]. However, to date the underlying mechanism as to why its (0001) surface exhibits an anomalously large electron-phonon coupling effect (λ_e-ph^s≈1.0) 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 λ_e-ph^s 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 λ_e-ph^s 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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