Influence of lithium doping on the thermodynamic properties of graphene based superconductors

The superconducting phase in graphene can be induced by doping its surface with lithium atoms. In this paper, it is shown that the critical temperature (TC) for the LiC6 and Li2C6 compounds changes from 8.55 K to 21.83 K. The other thermodynamic parameters--the order parameter (Δ), the specific heat for the superconducting (C(S)) and the normal (C(N)) state and the thermodynamic critical field (HC)--differ from the predictions of the Bardeen-Cooper-Schrieffer theory. In particular, the ratio RΔ ≡ 2Δ(0)/kBTC is equal to[3.72]LiC6 and [4.21]Li2C6. Additionally, the quantities RC ≡ ΔC(TC)/C(N)(TC) and [Formula: see text] take the values[1.47]LiC6,[1.79]Li2C6 and [0.167]LiC6, [0.144]Li2C6. Finally, it is shown that the electron effective mass at TC is high and equals:[1.61me]LiC6 and [2.12me]Li2C6.