Strongly correlated doped hole carriers in the superconducting nickelates: Their location, local many-body state, and low-energy effective Hamiltonian

The families of high-temperature superconductors recently welcomed a new member: hole-doped nickelate Nd0.8Sr0.2NiO2 with a similar to 15 K transition temperature. To understand its emergent low-energy behaviors and experimental properties, an immediate key question is whether the superconducting hole carriers reside in oxygen as in the cuprates or in nickel as in most nickelates. We answer this crucial question via a (LDA + U)+ED scheme: deriving an effective interacting Hamiltonian of the hole carriers from density functional LDA + U calculation and studying its local many-body states via exact diagonalization. Surprisingly, distinct from the expected Ni2+ spin-triplet state found in most nickelates, the local ground state of two holes is actually a Ni-O spin-singlet state with the second hole greatly residing in oxygen. The emerged eV-scale model therefore resembles that of the cuprates, advocating further systematic experimental comparisons. Tracing the microscopic origin of this unexpected result to the lack of apical oxygen in this material, we proposed a route to increase superconducting temperature and a possible quantum phase transition absent in the cuprates.

Automated summary

By studying the hole carriers in the new member of high-temperature superconductors, Nd0.8Sr0.2NiO2, it was found that the holes mainly reside in oxygen, similar to the cuprates. This unexpected result suggests a possible route to increase superconducting temperature and a quantum phase transition absent in cuprates.