Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors. arXiv submission processing window: times are unavailable (UTC).

1. Electronic structure and correlation of La$_4$Co$_2$NiO$_8$Cl$_2$: a theoretical proposal for a La$_4$Ni$_3$O$_{10}$-like high-temperature superconductor

Summary: Building on the discovery of high-pressure superconductivity in trilayer nickelate La₄Ni₃O₁₀, this study employed density functional theory combined with dynamical mean-field theory (DFT+DMFT) to design and calculate the cobalt-based analogue La₄Co₂NiO₈Cl₂. By substituting the inner-layer Co in the high-pressure phase La₄Co₃O₁₀ with Ni and incorporating Cl to achieve electron doping, this compound acquires a crystal structure and strongly correlated electronic characteristics similar to those of superconducting La₄Ni₃O₁₀: the outer-layer Co orbitals exhibit strong effective mass enhancement and non-Fermi liquid behavior, while the inner-layer Ni behaves as a weakly correlated Fermi liquid; a flat band near the Fermi level originating from the outer-layer Co orbitals emerges around the M point; and there is pronounced orbital selectivity as well as local spin fluctuations mixing high-spin and low-spin states. These features are in close agreement with the key electronic states of La₄Ni₃O₁₀, indicating that La₄Co₂NiO₈Cl₂ is a promising candidate for realizing high-temperature superconductivity in cobalt-based layered compounds, providing a theoretical basis for subsequent experimental exploration.

2. Detecting pairing symmetry of bilayer nickelates using electronic Raman scattering

Summary: Using a two-orbital bilayer model, this study systematically calculates the electronic Raman response in different Raman channels via both multiorbital and band-sum methods to distinguish the controversial pairing symmetry in the bilayer nickelate superconductor La₃Ni₂O₇. By comparing the Raman susceptibilities obtained from the multiorbital approach and the band-sum approximation, it is found that the Raman response can effectively differentiate various pairing symmetries and identify the Fermi-pocket-dependent gap sizes in fully gapped and nodal superconducting states. Specifically, nodal dₓ²⁻ᵧ²/dₓᵧ-wave pairing exhibits robust power-law behavior at low energies, distinctly different from fully gapped pairing; for s±-wave pairing, detailed gap anisotropy on the β pocket can be determined. The study also emphasizes the crucial role of multiorbital effects in shaping the Raman spectra, and points out that electronic Raman scattering, as a symmetry-resolving probe, provides a powerful means to determine the superconducting gap structure of unconventional superconductors, offering significant experimental implications for understanding the superconducting mechanism of bilayer nickelates.