Electron-phonon coupling and superconductivity in graphene

We have performed an high-resolution ARPES investigation to try to find an electron donor for graphene that is capable of inducing strong electron–phonon coupling and superconductivity. Calcium is the most promising candidate for realizing superconductivity in graphene.

Fedorov et al., Nat. Commun. 5, 3257 (2014);    Haberer et al., Phys. Rev. B 88, 081401(R) (2013).

High-resolution ARPES was carried out on Cs, Rb, K, Na, Li, and Ca doped graphene. For each dopant we determine the full electronic band structure, the Eliashberg function, and the superconducting critical temperature Tc from the spectral function. From a self-energy analysis we find an anisotropic electron-phonon coupling (EPC) parameter for the KΓ (KM) high-symmetry directions in momentum space, respectively. Interestingly, the high-energy part of the Eliashberg function which relates to graphene's optical phonons is equal in both directions but only in KM does appear an additional low-energy peak for all dopants with an energy and intensity that depend on the dopant atom. The low energy and high intensity of this peak are crucially important for achieving superconductivity. Calcium doped graphene should have the highest superconducting critical temperature of about 1.5 K.

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Observation of a universal donor-dependent vibrational mode in graphene
A.V. Fedorov, N.I. Verbitskiy, D. Haberer, C. Struzzi, L. Petaccia, D. Usachov, O.Y. Vilkov, D.V. Vyalikh, J. Fink, M. Knupfer, B. Büchner, A. Grüneis,
Nat. Commun. 5, 3257 (2014).
doi: 10.1038/ncomms4257

This paper was selected as an Elettra Top Story.

f Anisotropic Eliashberg function and electron-phonon coupling in doped graphene
D. Haberer, L. Petaccia, A.V. Fedorov, C.S. Praveen, S. Fabris, S. Piccinin, O. Vilkov, D.V. Vyalikh, A.  Preobrajenski, N.I. Verbitskiy, H. Shiozawa, J. Fink, M. Knupfer, B. Büchner, A. Grüneis,
Phys. Rev. B 88, 081401(R) (2013).
doi: 10.1103/PhysRevB.88.081401
Last Updated on Monday, 24 July 2023 18:04