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TT: Fachverband Tiefe Temperaturen
TT 69: Focus Session: Nickelate Superconductivity: Insights into Unconventional Pairing and Correlation Effects II (joint session TT/DS/MA)
TT 69.11: Vortrag
Donnerstag, 12. März 2026, 12:15–12:30, HSZ/0003
Incommensurate spin-fluctuations and competing pairing symmetries in La3Ni2O7 — •Han-Xiang Xu1 and Daniel Guterding2 — 1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China — 2Technische Hochschule Brandenburg, Brandenburg an der Havel, Germany
The discovery of superconductivity in the bilayer nickelate La3Ni2O7 under high pressure raises key questions about the pairing symmetry and microscopic mechanism. Using a three-dimensional multi-orbital Hubbard model including all Ni 3d and O 2p states, we analyze the superconducting instability within the random phase approximation. Spin fluctuations with incommensurate wave vectors (π/2,π/2) and (7π/10,7π/10) coexist and compete, leading to nearly degenerate sign-changing s±- and dx2−y2-wave pairing channels. The leading symmetry depends sensitively on pressure and the ratio of Hund’s rule to Coulomb interactions. Cooperative incommensurate fluctuations stabilize a dx2−y2-wave state for realistic parameters, while their competition may explain the absence of magnetic order. These findings reconcile previous contradictory results and highlight the importance of careful model construction for bilayer nickelates.
[1] H.-X. Xu and D. Guterding, arXiv:2501.05254
Keywords: superconductivity; nickelates; spin fluctuations; pairing symmetry; random phase approximation