High-Tc superconductivity by mobilizing local spin singlets and possible route to higher Tc in pressurized La3Ni2O7

Abstract

We clarify the pairing mechanism of high-Tc superconductivity in bilayer La3Ni2O7 under high pressure by employing the static auxiliary field Monte Carlo approach to simulate a minimal effective model that contains local dz2 interlayer spin singlets and metallic dx2−y2 bands. Superconductivity is induced when the local spin singlet pairs are mobilized and attain long-distance phase coherence by hybridization with the metallic bands. When projected onto realistic Fermi surfaces, it yields a nodeless s-wave gap on the γ Fermi surface, and extended s-wave gaps of the same (opposite) sign on the α (β) Fermi surface due to its bonding (antibonding) character, with nodes or gap minima along the diagonal direction of the two-dimensional Brillouin zone. We find a dual role of the hybridization that not only induces global phase coherence but also competes with the spin singlet formation. This leads to a tentative phase diagram where Tc varies nonmonotonically with the hybridization, in good correspondence with experimental observations. A roughly linear relation is obtained for realistic hopping and hybridization parameters: Tc≈0.04−0.05J, where J is the interlayer superexchange interaction. We emphasize the peculiar tunability of the bilayer structure and propose that Tc may be further enhanced by hole doping or applying uniaxial pressure along the c axis on superconducting La3Ni2O7. Our work provides reliable numerical evidence for the pairing mechanism of high-Tc superconductivity in La3Ni2O7 and points out a potential route to achieve even higher Tc.

Source-reported materials — not catalogue approval

Similar papers