Pairing symmetry in BiS₂-based superconductors

The possible pairing symmetries for BiS$_{2}-$based superconductors is investigated by using a minimal two-orbital model with onsite and nearest-neighbor intraorbital attractions $V_{0}$ and $V_{1}$, respectively. By using the mean-field approximation and solving the self-consistent equations, the phase diagram of the pairing symmetry is obtained. It is shown that the model allows three possible pairing symmetries, depending on the values of $V_{0}$ and $V_{1}$: the isotopic $s-$wave pairing [$\Delta_{\mathbf{k}}=\Delta_{s}$], the anisotropic $s-$wave pairing [$\Delta_{\mathbf{k}}=\Delta_{s}+\frac{\Delta_{xs}}{2}(\cos k_{x}+\cos k_{y})$] and the $d-$wave pairing [$\Delta_{\mathbf{k}}=\frac{\Delta_{d}}{2}(\cos k_{x}-\cos k_{y})$]. Furthermore the density of states for these pairing symmetries exhibit different behaviors which can be used to distinguish them.