Electronic Correlation and Pseudogap-Like Behavior of High-Temperature Superconductor La3Ni2O7.

High-temperature superconductivity (HTSC) remains one of the most challenging and fascinating mysteries in condensed matter physics. Recently, superconductivity with transition temperature exceeding liquid-nitrogen temperature is discovered in La₃Ni₂O₇ at high pressure, which provides a new platform to explore the unconventional HTSC. In this work, using high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structures of La₃Ni₂O₇ at ambient pressure. Our experiments are in nice agreement with ab initio calculations after considering an orbital-dependent band renormalization effect. The strong electron correlation effect pushes a flat band of d _{z ²} orbital component below the Fermi level (E _F), which is predicted to locate right at E _F under high pressure. Moreover, the d _{x ²– y ²} band shows pseudogap-like behavior with suppressed spectral weight and diminished quasiparticle peak near E _F. Our findings provide important insights into the electronic structure of La₃Ni₂O₇, which will shed light on understanding of the unconventional superconductivity in nickelates. [ABSTRACT FROM AUTHOR]