A possible new family of unconventional high temperature superconductors

We suggest a new family of Co/Ni-based materials that may host unconventional high temperature superconductivity (high-T_c). These materials carry layered square lattices with each layer being formed by vertex-shared transition metal tetrahedra cation-anion complexes. The electronic physics in these materials is determined by the two dimensional layer and is fully attributed to the three near degenerated t_2gd-orbitals close to a d⁷ filling configuration in the d-shell of Co/Ni atoms. The electronic structure meets the necessary criteria for unconventional high T_c materials proposed recently by us to unify the two known high-T_c families, cuprates and iron-based superconductors. We predict that they host superconducting states with a d-wave pairing symmetry with T_c potentially higher than those of iron-based superconductors. These materials, if realized, can be a fertile new ground to study strongly correlated electronic physics and provide decisive evidence for superconducting pairing mechanism.