Correlation effects and concomitant two-orbital s± -wave superconductivity in La3Ni2O7 under high …

High-${T}_{c}$ superconductivity (SC) has been found experimentally in the bilayer material ${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$ under high pressure recently, in which the Ni-$3{d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ and $3{d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ orbitals are expected to play a key role in the electronic structure and the SC. Here we study the two-orbital electron correlations and the nature of the SC in the framework of the dynamical mean-field theory using the bilayer two-orbital Hubbard model downfolded from the band structure of ${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$. We find that each of the two orbitals forms ${s}_{\ifmmode\pm\else\textpm\fi{}}$-wave SC pairing. Because of the interorbital hoppings, the two-orbital SCs are concomitant, and furthermore they transition to Mott insulating states simultaneously when tuning the system to half filling. The Hund's coupling induced local interorbital spin coupling enhances the electron correlations pronouncedly and is crucial to the SC.