Year: 2026
Type: preprint
Abstract: We investigate the superconducting pairing symmetry and its doping evolution in pressurized La$_3$Ni$_2$O$_7$. For the undoped compound, the most favorable pairing state is found to be $s_{\pm}$-wave, characterized by sign reversal of the gap functions between the Fermi pockets. A detailed analysis of the pairing interactions reveals that this unconventional state originates from repulsive interactions mediated by the magnetic odd modes of the bilayer nickelate. Upon hole doping, the $γ$ Fermi pocket expands, which amplifies the intrapocket repulsions on this pocket. These repulsions, driven by the magnetic even modes, gradually dominates the pairing interactions and ultimately drive a transition in pairing symmetry from $s_{\pm}$-wave to $d_{xy}$-wave in the heavily hole-doped regime. In stark contrast, the $s_{\pm}$-wave pairing persists under electron doping, even deep into the heavily electron-doped regime where a Lifshitz transition occurs. This finding suggests that the $γ$ Fermi pocket is not essential for the emergence of superconductivity in bilayer nickelates. In fact, the $s_{\pm}$-wave pairing becomes more robust in the absence of the $γ$ pocket, as spin fluctuations are strongly enhanced by the favorable nesting between the $α$ and $β$ pockets --- a condition guaranteed by Luttinger's theorem and the Fermi surface topology. We believe that exploring the doping evolution of superconducting pairing will open a new realm for testing the pairing mechanism in pressurized La$_3$Ni$_2$O$_7$.
Source: arXiv (Cornell University)
Authors: Zhang, Hai-Yang, Bai, Yu-Jie, Kong, Fan-Jie
Institution: Yancheng Institute of Technology
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G4795618029, G8491541954
OpenAlex ID: W7204947788