Existence and role of the γ Fermi-surface pocket in La3Ni2O7

Ascertain whether a γ-band–derived Fermi-surface pocket at the Brillouin-zone corner crosses the Fermi level in pressurized La3Ni2O7 and establish whether this pocket is integral to the occurrence of high-temperature superconductivity in the high-pressure phase.

Background

The bilayer La3Ni2O7 electronic structure is dominated by Ni eg orbitals producing multiple bands (α, β, γ, δ). Calculations using different exchange-correlation treatments (GGA vs. hybrid functionals) disagree on whether the γ band crosses the Fermi level, leading to contrasting Fermi-surface topologies.

Because superconductivity may depend sensitively on such topology, clarifying the existence of the γ pocket and its contribution is essential. The authors explicitly note that this point remains under debate and that decisive experiments are required to test the conjectured importance of the γ pocket.

References

The presence of a γ-FS at the BZ corner crossing the Fermi level remains under debate .

— Recent progress in nickelate superconductors  (2509.08386 - Wang et al., 10 Sep 2025) in Figure 6(b) caption; Section 3.2 Electronic structure and apical oxygen vacancy

Nevertheless, the existence of the γ pocket in 327 thin films at ambient pressure remains debated, both experimentally[20-22] and theoretically[23-27].

— Weak coupling theory of nickel-based 327 superconductors  (2608.22759 - Jianjian et al., 24 Aug 2026) in Section 2, “Multi-orbital Hubbard Model”