Ternary nickel hydrides: a new platform for unconventional superconductivity and quantum magnetism

TL;DR

This paper introduces ternary nickel hydrides as a new class of materials that exhibit properties similar to cuprates, with potential for unconventional superconductivity and quantum magnetism, due to their unique electronic structure and magnetic interactions.

Contribution

It proposes and analyzes ternary nickel hydrides MNiH2 as novel materials with properties akin to cuprates but with distinct electronic and magnetic features, highlighting their potential for superconductivity.

Findings

Ni-H bands are wider than in oxides due to shorter bonds.

Charge transfer energy is smaller than in LaNiO2, implying higher Tc.

NaNiH2 may be metallic and superconducting without doping.

Abstract

In this letter, we propose ternary nickel hydrides MNiH2 (M = Li, Na) as new materials that mimic cuprate physics but have important differences and interesting properties. Ni-H bands are wider than in oxides due to shorter bond lengths and covalency is larger than in Ni oxides which leads to a large scale of magnetic interactions. The charge transfer energy is smaller than in LaNiO2 which in cuprates translates to a larger Tc. We notice the formation of the electride band close to the Fermi surface which appears due to H vacancy along the c lattice vector. The considerable difference with cuprates arises from dz2 orbitals hybridization with interstitial orbitals allowing charge transfer to an apical vacancy state and self-doping the cuprate like Ni dx2-y2 H s antibonding bands which suggests that stoichiometric NaNiH2 may already be metallic and superconducting.