2026/07/21 by Wiktoria Lewandowski, Steffen Bötzel, Ilya M. Eremin +1
#cond-mat.str-el #cond-mat.supr-con
The La2NiO4 compound stabilizes in nature in the so-called T structure with octahedral oxygen coordination of the Ni site. Motivated by a similarly existing polymorph for La2CuO4 in the cuprate system, we here study La2NiO4 in the T^′-structure with square-planar oxygen coordination of Ni by means of first-principles many-body theory. The hypothetical T^′-La2NiO4 compound turns out to be a manifest charge-transfer insulator with a cuprate-like charge gap of ∼ 1.8 eV. Upon doping, a strong carrier asymmetry is revealed, i.e. while holes dominantly enter O(2p)-derived states, electrons may become itinerant majorly within effective Ni-dx2-y2 states. Nearest-neighbor antiferromagnetic ordering at stoichiometry appears absent in the T^′ structure, in stark contrast to the strong antiferromagnetism in the T structure. Our theoretical study opens up new pathways for correlation physics in layered nickelates with challenging charge-transfer signatures, awaiting experimental inquiries.