  Recently discovered superconductivity in hole-doped nickelate
Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ caught intensive attention in the field. An
immediate question is how to improve its superconducting properties. Guided by
the key characteristics of electronic structures of the cuprates and the
nickelates, we propose that nickel chalcogenides with a similar lattice
structure should be a promising family of materials. Using NdNiS$_2$ as an
example, we find this particular crystal structure a stable one, through
first-principle structural optimization and phonon calculation. We justify our
proposal by comparing with CaCuO$_2$ and NdNiO$_2$ the strength of the
charge-transfer characteristics and the trend in their low-energy many-body
effective Hamiltonians of doped hole carriers. These analysis indicates that
nickel chalcogenides host low-energy physics closer to that of the cuprates,
with stronger magnetic interaction than the nickelates, and thus deserve
further experimental exploration. Our proposal also opens up the possibility of
a wide range of parameter tuning through ligand substitution among
chalcogenides, to further improve superconducting properties.
