High-TC superconductivity in La3Ni2O7 based on the bilayer two-orbital t-J model

Abstract The recently discovered high- T c superconductor La 3 Ni 2 O 7 has sparked renewed interest in unconventional superconductivity. Here we study superconductivity in pressurized La 3 Ni 2 O 7 based on a bilayer two-orbital t − J model, using the renormalized mean-field theory. Our results reveal a robust s ± -wave pairing driven by the inter-layer $${d}_{{z}^{2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>d</mml:mi></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>z</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:msub></mml:math> magnetic coupling, which exhibits a transition temperature within the same order of magnitude as the experimentally observed T c ~ 80 K. We establish a comprehensive superconducting phase diagram in the doping plane. Notably, the La 3 Ni 2 O 7 under pressure is found to be situated roughly in the optimal doping regime of the phase diagram. When the $${d}_{{x}^{2}-{y}^{2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>d</mml:mi></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>x</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup><mml:mo>−</mml:mo><mml:msup><mml:mrow><mml:mi>y</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:msub></mml:math> orbital becomes close to half-filling, d -wave and d + i s pairing can emerge from the system. We discuss the interplay between Fermi surface topology and different pairing symmetries. The stability of the s ± -wave pairing against Hund’s coupling and other magnetic exchange couplings is discussed.