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.