Origin of the diagonal double-stripe spin density wave and potential superconductivity in bulk La3Ni2O7 at ambient pressure

Abstract

The discovery of high-temperature superconductivity (SC) with Tc≈80 K in the pressurized La3Ni2O7 has aroused great interest. Currently, due to technical difficulties, most experiments on La3Ni2O7 can only be performed at ambient pressure. Particularly, various experiments have revealed the presence of a spin density wave (SDW) in the unidirectional diagonal double-stripe pattern with wave vector near ±(π/2,π/2) in La3Ni2O7 at ambient pressure. In this work, we employ first-principles calculations followed by the random phase approximation (RPA)-based study to clarify the origin of this special SDW pattern and the potential SC in La3Ni2O7 at ambient pressure. Starting from our density-functional-theory band structure, we construct an eight-band bilayer tight-binding model using the Ni−3dz2 and 3dx2−y2 orbitals, which is equipped with the standard multiorbital Hubbard interaction. Our RPA calculation reveals an SDW order driven by Fermi surface nesting with wave vector Q≈(0,±0.84π) in the folded Brillouin zone. From the view of the unfolded Brillouin zone, the wave vector turns to Q0≈±(0.58π,0.58π), which is near the one detected by various experiments. Further more, this SDW exhibits an interlayer antiferromagnetic order with a unidirectional diagonal double-stripe pattern, consistent with recent soft x-ray scattering experiments. This result suggests that the origin of the SDW order in La3Ni2O7 at ambient pressure can be well understood in the itinerant picture as driven by Fermi surface nesting. In the aspect of SC, our RPA study yields an approximate s±-wave spin-singlet pairing with Tc much lower than that under high pressure. Furthermore, the Tc can be strongly enhanced through hole doping, leading to possible high-temperature SC at ambient pressure.

Source-reported materials — not catalogue approval

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