Superconductivity and Electron-Phonon Coupling in Graphite Intercalation Compunds

摘要: In graphite intercalation compounds (GIC), the of various atomic or molecular species in between graphene layers leads to novel properties and a very rich physics, including superconductivity (Dresselhaus & Dresselhaus, 2002). intercalated with alkaline metals, has been known for decades (Hannay et al., 1965), but after recent discovery relatively high Tc CaC6 (Tc = 11.5 K)(Emery 2005; Weller 2005) research this field intensified. conventional electron-phonon coupling long be pairing interaction responsible superconductivity. The strength essentially determines superconducting transition temperature Tc. Even though is most likely GICs (Hinks 2007; Kim 2006; Lamura 2006), it still not clear what electronic states, intercalantor graphenederived ones, phonons are (Boeri Calandra M Mazin Mazin, 2005). Due differences structure composition, no trends have identified that could unambiguously resolve these issues. For example, KC8 superconductor LiC6 not. Further, earths, ranges from zero 11.5K, even they share same chemical formula MC6, where an earth atom. This obviously represents serious problem proposal originates sheets only role intercalants provide charge bands. band calculations show GICs, interlayer state exists above π∗ (Holzwarth 1984; Posternak 1983), prompting some researchers propose its partial filling soft intercalant induces (Csanyi experimental situation inconclusive, strong advocates 2007) dominated (Dean 2010; Gruneis 2009; Pan Valla 2009). Recent angle resolved photoemission spectroscopy study on (Valla 2009) reported graphene-derived Fermi surface enough explain range tens Kelvin, indicating crucial ingredients GICs. However, test idea, would important extend similar studies different One manifestation renormalization dispersion "kink" at energy scale associated phonons. Superconductivity Electron-Phonon Coupling Graphite Intercalation Compunds 19