Daily Overview: Today’s highlighted work focuses on an in-depth understanding of the electronic structure of mixed Ruddlesden–Popper nickelates, in particular the theoretical characterization of the competition between superconducting pairing symmetries in the bilayer nickelate La₃Ni₂O₇. Roy and Coleman treat a simplified bilayer t-J model of La₃Ni₂O₇ within a mean-field fractionalization scheme that retains the full SU(2) particle–hole symmetry of the half-filled t-J model, targeting the competition between s± and cuprate-like d-wave pairing symmetries; the authors point out that a conventional U(1) treatment does not fully incorporate Coulomb repulsion and the no-double-occupancy constraint, whereas an additional Coulomb pseudopotential introduced by the fractionalization method suppresses s± pairing (i.e., the case in which the pairing amplitude has the opposite sign) and favors d-wave pairing, thereby theoretically indicating that interlayer coupling and the local no-double-occupancy condition can alter the competition between pairing symmetries in La₃Ni₂O₇. It should be emphasized that the above understanding—that the pseudopotential suppresses s±, favors d-wave, and that interlayer coupling and the no-double-occupancy condition affect the pairing competition—is a mean-field theoretical prediction rather than an experimentally established pairing mechanism. arXiv submission processing window: 2026-10-27 00:00 to 2026-10-27 00:00 UTC.

1. The fate of $s_{\pm}$ superconductivity in the bilayer nickelate La$_3$Ni$_2$O$_7$

Summary: This paper addresses the pairing-symmetry problem of high-temperature superconductivity in the bilayer nickelate La₃Ni₂O₇; against the theoretical background of competition between s± and copper-oxide-like d-wave pairing, it constructs a mean-field fractionalization scheme that preserves the full SU(2) particle-hole symmetry of the half-filled t-J model and applies it to a simplified bilayer t-J model of La₃Ni₂O₇. The authors note that the conventional U(1) treatment does not fully incorporate Coulomb repulsion and the constraint prohibiting double occupancy, whereas the fractionalization method introduces an additional Coulomb pseudopotential constraint. Calculations show that this pseudopotential suppresses s± pairing and favors d-wave pairing, theoretically indicating that interlayer coupling and the local no-double-occupancy condition can alter the pairing-symmetry competition in La₃Ni₂O₇; this conclusion is a mean-field theoretical prediction, not an experimentally established pairing mechanism.