Superconducting Phases in Lithium Decorated Graphene LiC 6

Title	Superconducting Phases in Lithium Decorated Graphene LiC 6
Authors	Rouhollah Gholami, Rostam Moradian, Sina Moradian, Warren E. Pickett
Date	04/10/2018
Introduction	This detailed investigation centres on the potential superconducting phases within graphene. A realistic tight binding model, carefully aligned with ab initio calculations, precisely accounts for graphene's lithium decoration, which introduces broken lattice symmetry. This model incorporates s and d symmetry Bloch character, influencing the resultant gap symmetries. The analysis reveals seven hybridised lithium-carbon orbitals supporting nine distinct bond pairing amplitudes. The gap equation is resolved for all possible gap symmetries. One specific band exhibits weak dispersion near the Fermi energy along the Γ→M direction, where its Bloch wave function comprises a linear combination of dx2−y2 and dxy character. This band is responsible for dx2−y2 and dxy pairing, exhibiting the lowest pairing energy in the presented model. These symmetries largely retain characteristics observed in a two-band model of pristine graphene. Additionally, a segment of this band, along K→Γ, is nearly degenerate with an upper s band, promoting extended s-wave pairing—a phenomenon not observed in the two-band model. Electron doping to a critical chemical potential of μ1=0.22eV initially decreases the pairing potential, which then increases until a second critical value of μ2=1.3 eV. At this point, a phase transition occurs, leading to a new phase absent in the two-band model. This phase in pristine graphene transforms into the conventional extended s-wave pairing.
Quote	Rouhollah Gholami, Rostam Moradian and Sina Moradian et al. Superconducting Phases in Lithium Decorated Graphene LiC 6. 2018.
Element	Lithium (Li) , Carbon (C)
Industry	Research & Laboratory