Evidence for superconductivity in Li-decorated monolayer graphene

• Published in: arXiv.org 2015-08
• Main Authors: Ludbrook, Bart, Levy, Giorgio, Nigge, Pascal, Zonno, Marta, Schneider, Michael, Dvorak, David, Veenstra, Christian, Zhdanovich, Sergey, Wong, Douglas, Pinder Dosanjh, Straßer, Carola, Stohr, Alexander, ti, Stiven, Ast, Christian, Starke, Ulrich, Damascelli, Andrea
• Format: Article
• Language: English
• Subjects: Adatoms; Coupling; Decoration; Electrons; Fermi surfaces; Graphene; Lithium; Monolayers; Phonons; Photoelectric emission; Superconductivity; Superlattices; Temperature dependence
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1508.05925

Monolayer graphene exhibits many spectacular electronic properties, with superconductivity being arguably the most notable exception. It was theoretically proposed that superconductivity might be induced by enhancing the electron-phonon coupling through the decoration of graphene with an alkali adatom superlattice [Profeta et al. Nat. Phys. 8, 131-134 (2012)]. While experiments have indeed demonstrated an adatom-induced enhancement of the electron-phonon coupling, superconductivity has never been observed. Using angle-resolved photoemission spectroscopy (ARPES) we show that lithium deposited on graphene at low temperature strongly modifies the phonon density of states, leading to an enhancement of the electron-phonon coupling of up to \(\lambda\!\simeq\!0.58\). On part of the graphene-derived \(\pi^*\)-band Fermi surface, we then observe the opening of a \(\Delta\!\simeq\!0.9\) meV temperature-dependent pairing gap. This result suggests for the first time, to our knowledge, that Li-decorated monolayer graphene is indeed superconducting with \(T_c\!\simeq\!5.9 K\).