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تسجيل مستخدم جديدUnderlying topological Dirac nodal line mechanism of anomalously large electron-phonon coupling strength on Be (0001) surface
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Beryllium was recently discovered to harbor a Dirac nodal line (DNL) in its bulk phase and the DNL-induced non-trivial drumhead-like surface states (DNSSs) on its (0001) surface, rationalizing several already-existing historic puzzles [Phys. Rev. Lett., textbf{117}, 096401 (2016)]. However, to date the underlying mechanism, as to why its (0001) surface exhibits an anomalously large electron-phonon coupling effect ($lambda_{e-ph}^s$ $approx$ 1.0), remains unresolved. Here, by means of first-principles calculations we have evidenced that the coupling of the DNSSs with the phononic states mainly contributes to its novel surface emph{e-ph} enhancement. Besides that the experimentally observed $lambda_{e-ph}^s$ and the main Eliashberg coupling function (ECF) peaks have been reproduced well, we have decomposed the ECF, $alpha^{2}$$F$(emph{k},textbf{emph{q}};emph{v}), and the emph{e-ph} coupling strength $lambda(emph{k},textbf{emph{q}};emph{v})$ as a function of each electron momentum (emph{k}), each phonon momentum (textbf{emph{q}}) and each phonon mode ($v$), evidencing the robust connection between the DNSSs and both $alpha^{2}$$F$(emph{k},textbf{emph{q}};emph{v}) and $lambda(emph{k},textbf{emph{q}};emph{v})$. The results reveal the strong emph{e-ph} coupling between the DNSSs and the phonon modes, which contributes over 80$%$ of the $lambda_{e-ph}^s$ coefficient on the Be (0001) surface. It highlights that the anomalously large emph{e-ph} coefficient on the Be (0001) surface can be attributed to the presence of its DNL-induced DNSSs, clarifying the long-term debated mechanism.
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