Spin-charge separation and unconventional superconductivity in t-J model on honeycomb lattice

The physical nature of doped Mott-insulator has been intensively studied for more than three decades. It is well known that the single band Hubbard model or t-J model on bipartite lattice is the simplest model to describe a Mott-insulator. Unfortunately, the key mechanism of superconductivity in these toy models is still under controversial so far. Here we propose a new mechanism for the d+id-wave superconductivity (SC) that occurs in the low-doping region of the honeycomb lattice t-J model based on Grassmann tensor product state simulation and spin-charge separation formulation. Moreover, in the presence of anti-ferromagnetic order, a continuum effective field theory for the holons near half-filling is developed, and it reveals the compitition between attractive and repulsive holon interactions induced by the exchange of spinons and gauge fluctuations, respectively. At a large value of t/J, the repulsive interaction dominates, leading to the non-Fermi liquid behavior; while in a moderate range of t/J, the attraction dominates and leads to the superconducting order. Possible experimental detection of spin-charge separation phenomena are also discussed.