Orbital-dependent electron correlation in double-layer nickelate La₃Ni₂O₇.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• High-temperature superconductivity near 80 K in La₃Ni₂O₇ under high pressure has garnered significant research interest.
• Understanding the electronic structure is critical for developing theories explaining superconductivity in nickelates, yet this data has been largely unavailable.

Purpose of the Study:

• To experimentally determine the electronic band structures of La₃Ni₂O₇.
• To provide crucial data for theoretical models of high-temperature superconductivity in this material.

Main Methods:

• High-resolution angle-resolved photoemission spectroscopy (ARPES) was employed for direct measurement.
• Experimental results were compared with theoretical band structure calculations.

Main Results:

• The Fermi surface and band structures of La₃Ni₂O₇ were successfully observed.
• Strong electron correlations were identified, showing dependence on orbital character and momentum.
• A flat band, originating from Ni-3d orbitals near the zone corner and approximately 50 meV below the Fermi level, exhibited the most significant electron correlation.

Conclusions:

• The observed electronic structures provide essential experimental insights into La₃Ni₂O₇.
• The findings support theoretical proposals linking the flat Ni-3d band to the emergence of superconductivity.
• This work lays the groundwork for a deeper understanding of high-temperature superconductivity mechanisms in nickelate materials.