English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Superconductivity found in doped NdNiO$_2$ is puzzling as two localsymmetries of doped NiO$_2$ layers compete, with presumably far-reachingimplications for the involved mechanism: a cuprate-like regime with Zhang-Ricesinglets {\cblue is replaced by local triplet states at realistic values ofcharge-transfer energy, which would suggest a rather differentsuperconductivity scenario from high-$T_c$ cuprates}. We address thiscompetition by investigating Ni$_4$O$_8$ clusters with periodic boundaryconditions in the parameter range relevant for the superconducting nickelates.With increasing value of charge-transfer energy we observe upon hole doping theexpected crossover from the cuprate regime dominated by Zhang-Rice singlets tothe local triplet states. We find that smaller charge-transfer energy $\Delta$is able to drive this change of the ground state character when realisticvalues for nickel-oxygen repulsion $U_{dp}$ are taken into account. For largevalues of the charge-transfer energy, oxygen orbitals are less important thanin superconducting cuprates as their spectral weight is found only at ratherhigh excitation energies. However, a second Ni($3d$) orbital can easily becomerelevant, with either the $xy$ or the $3z^2-r^2$ orbitals contributing inaddition to the $x^2-y^2$ orbital {\cblue to the formation of triplet states.In addition,} our result that $U_{dp}$ (acting between Ni and O) favors onsitetriplets implies that correlation effects beyond purely onsite interactionsshould be taken into account when obtaining effective two-band models.

Interplay between Zhang-Rice singlets and high-spin states in a model for doped NiO$_2$ planes