Description
Cuprate high-temperature superconductors emerge from an unusual metallic state characterized by Fermi arcs, pseudogap opening, and marginal-Fermi-liquid behavior. Whether these anomalous normal-state properties are universal among high-temperature superconductors remains a central unresolved issue. Infinite-layer nickelates, widely regarded as cuprate analogs, provide a key platform for addressing this question.
Here we investigate optimally doped La0.8Ca0.2NiO2 and parent LaNiO2 thin films using angle-resolved photoemission spectroscopy. By achieving high crystalline and surface quality, we resolve clear quasiparticle peaks near the (π/2, π/2) region at optimal doping. The imaginary part of the electronic self-energy shows a linear energy dependence, indicative of marginal-Fermi-liquid behavior reminiscent of the hole-doped cuprates. As found in cuprates, pronounced momentum-dependent suppression of the near-EF density of states is found here, with enhanced scattering and stronger correlations near (π, 0). However, in contrast to the Fermi-arc behavior observed in underdoped cuprates, finite spectral weight remains near (π, 0) in both LaNiO2 and La0.8Ca0.2NiO2. These results reveal both commonalities and distinctions between infinite-layer nickelates and cuprates, showing that cuprate-like anisotropic correlations and marginal-Fermi-liquid behavior can emerge without invoking pseudogap formation or preformed Cooper
pairing.
