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Pressure and strain effects on the ab initio 𝐺⁡𝑊 electronic structure of La_3⁢Ni_2⁢O₇

The recent discovery of superconductivity in La₃⁢Ni₂⁢O₇ at a critical temperature above 80 K points to a nonconventional pairing mechanism in nickelates as in cuprates, possibly due to electronic correlations. We have calculated from first principles the electronic structure of La₃⁢Ni_2⁢O₇ under the effect of pressure and epitaxial strain including correlations by the 𝐺⁡𝑊 approximation to the many-body self-energy. We find that the Fermi surface is composed of a characteristic cuprate-shape sheet 𝛽 plus a nickelate-specific cylinder 𝛼, both from Ni 𝑒𝑔 orbitals, with a nonnegligible drop in the quasiparticle weight and an effective 1D character. This topology results from a delicate balance between the Ni-3⁢𝑑_𝑧2 hole pocket 𝛾, which is suppressed by correlations, and an emerging La-5⁢𝑑_{𝑥2−𝑦2} electron pocket induced by both correlation and pressure/strain effects and whose role at low energy has been neglected so far. Unlike cuprates, the electronic structure of La₃⁢Ni₂⁢O₇ is already correctly described from ab initio and in agreement with the experiment without the need to introduce adjustable parameters