Symmetry-Resolved Quasiparticle Dynamics and Electronic Correlations in Layered Nickelates across Density Wave Transitions

Since the recent discoveries of superconductivity and density wave (DW) orders in various layered nickelates, the microscopic origins of those electronic orders remain unresolved despite numerous research efforts. Using symmetry-resolved Raman spectroscopy, we investigate the evolution of electronic response at ambient pressure in both bilayer (La₃Ni₂O₇) and trilayer (La₄Ni₃O₁₀) nickelates. In both compounds, we uncover a systematic reduction of the incoherent electronic continuum across the DW transitions. In trilayer La₄Ni₃O₁₀, the DW gap formation manifests in the leading A_1g (s-wave) and the subdominant B_1g (d_x2-y2-wave) symmetry channels, which points to a partial removal of the Fermi surface in regions with predominant d_x2-y2 orbital characters. Moreover, we observe that the bilayer La₃Ni₂O₇ also exhibits a primary low-energy renormalization in the A_1g channel, but with notable differences in other symmetry-breaking channels. By providing a direct, symmetry-resolved view of the quasiparticle dynamics, our comparative investigation experimentally establishes key similarities and distinctions among La₄Ni₃O₁₀, La₃Ni₂O₇, and the cuprates, offering crucial insights into the nature of electronic correlations governing these high-temperature superconductors.