Ground-state and finite-temperature properties of spin liquid phase in the J1-J2 honeycomb model

In this paper we analyze the groundstate and finite-temperature properties of a frustrated Heisenberg $J_1-J_2$ model on a honeycomb lattice by employing the Schwinger boson technique. The phase diagram and spin gap as functions of $J_2\mathrm{/}{J}_1$ are presented, showing that the exotic spin liquid phase lies in $0.21<J_2\mathrm{/}{J}_1<0.43$. The temperature and magnetic-field dependences of specific heat, magnetic susceptibility and Knight shift are also presented. We find the spin liquid state is robust with respect to external magnetic field. These results provide clear information characterizing unusual properties of the exotic spin liquid phase for further experiments.