The recent discovery of high-Tcβ superconductivity in bilayer nickelate
La3βNi2βO7β under high pressure has stimulated great interest
concerning its pairing mechanism. We argue that the weak coupling model from
the almost fully-filled dz2β bonding band cannot give rise to its high
Tcβ, and thus propose a strong coupling model based on local inter-layer
spin singlets of Ni-dz2β electrons due to their strong on-site Coulomb
repulsion. This leads to a minimal effective model that contains local pairing
of dz2β electrons and a considerable hybridization with near
quarter-filled itinerant dx2βy2β electrons on nearest-neighbor sites.
The strong coupling between two components provides a composite scenario to
achieve high-Tcβ superconductivity. Our theory highlights the importance of
the bilayer structure of superconducting La3βNi2βO7β and points out
a potential route for the exploration of more high-Tcβ superconductors.Comment: 6 pages, 3 figure