Possibility of High Tc Superconductivity in doped Graphene

Graphene is at the forefront of condensed matter sciences, because of a variety of interesting phenomena it supports. If graphene could support high Tc superconductivity, after doping for example, it will make it even more valuable. Some authors have suggested possibility of superconductivity in graphite like systems. However, an early suggestion of one of us (Baskaran) was unique in the sense it combined Pauling's classic idea of resonating valence bond physics with band theory to obtain some exciting results for superconductivity. Black-Schaffer and Doniach took this approach further and found an unconventional d + id order parameter. To sharpen our theory and get more convincing and reliable results for superconductivity, we introduce a correlated variational BCS ground state wavefunction and perform extensive Monte Carlo study of the repulsive Hubbard model on the honeycomb lattice. We find that undoped graphene is not a superconductor, consistent with experiments and also mean field results. Interestingly, an appreciable superconducting order is obtained around an optimal doping. This result and a supportive slave particle analysis together suggest the possibility of high temperature superconductivity in doped graphene.