Cuprate-like electronic structures in infinite-layer nickelates with substantial hole dopings

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Infinite-layer (IL) nickelates are a new class of materials offering a platform for high-temperature superconductivity research.
• Understanding nickelate superconductivity is challenging due to complex electronic structures and a lack of direct experimental data.
• Previous studies relied on theoretical models, leading to controversial conclusions regarding the superconducting mechanism.

Purpose of the Study:

• To directly measure and analyze the electronic structures of parent and superconducting infinite-layer nickelates.
• To resolve the electronic structure complexities hindering the understanding of nickelate superconductivity.
• To compare the electronic properties of nickelates with those of cuprates.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was employed to probe the electronic states.
• The electronic structures of LaNiO2 (parent compound) and La0.8Ca0.2NiO2 (superconducting) were directly resolved.
• Fermi surface topology and band dispersion were analyzed.

Main Results:

• Direct measurement revealed quasi-2D hole and 3D electron pockets in the Fermi surfaces of both compounds.
• Doping with calcium (Ca) was observed to alter the volumes of these Fermi pockets.
• The hole pocket's topology and band dispersion resemble those in cuprates, but with significantly higher hole doping in the superconducting nickelate.

Conclusions:

• The electronic structure of infinite-layer nickelates exhibits unique characteristics compared to cuprates.
• Direct ARPES measurements provide crucial insights into the electronic states governing nickelate superconductivity.
• These findings advance the microscopic understanding of the infinite-layer nickelate family and its superconducting properties.