Proposal to improve Ni-based superconductors via enhanced charge transfer

TL;DR

This paper proposes that nickel chalcogenides, especially NdNiS$_2$, could serve as promising materials for high-temperature superconductivity due to their favorable electronic structures and charge-transfer characteristics, inspired by cuprates.

Contribution

The study introduces nickel chalcogenides as a new family of materials with potential for enhanced superconductivity, supported by first-principle calculations and comparative analysis.

Findings

NdNiS$_2$ is structurally stable and suitable for superconductivity.

Nickel chalcogenides have electronic properties closer to cuprates.

Potential for tuning superconducting properties via ligand substitution.

Abstract

Recently discovered superconductivity in hole-doped nickelate Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ has attracted 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, through first-principle structural optimization and phonon calculation, we find this particular crystal structure a stable one. We justify our proposal by comparing with CaCuO$_2$ and NdNiO$_2$ with regard to strength of the charge-transfer characteristics and the trend in their low-energy many-body effective Hamiltonians of doped hole carriers. This analysis indicates that nickel chalcogenides host low-energy physics closer to that of the cuprates, with stronger magnetic interaction than the nickelates, and thus they 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.