📝 SummarXiv

Abstract

Since the discovery of cuprate high-Tc superconductivity, numerous theoretical frameworks have been proposed; Anderson's RVB picture (Science 235, 1196-1198, 1987) and U(1) gauge theory (Phys. Rev. Lett. 76, 503-506, 1996) motivate a minimal one-band view that largely integrates out oxygen. By contrast, altermagnetism (Phys. Rev. X 12, 040501, 2022) yields a d-wave-like k-space magnetic texture from alternatingly rotated nonmagnetic cages; La2CuO4 (the parent of a high-Tc cuprate) is a prototypical example. As a proof of principle, we show in La2CuO4 that an alternating local pairing potential on the two Cu sublattices (plus/minus s(r)) produces a nodal, d-wave-like Delta(k). Since orthorhombic tilts are not the driver (and even suppress superconductivity in nickelates; Nature 621, 493, 2023), we then show that the in-plane oxygen sublattice of CuO2/NiO2 layers - ubiquitous in cuprates and nickelates - intrinsically realizes the same symmetry. Imposing an oxygen-centered, staggered s pairing yields a d-wave gap with perfect C4 symmetry, demonstrated self-consistently in NdNiO2 from first principles. While the microscopic origin remains open, we outline possible scenarios, and our real-space construction maps directly onto lattice models, placing superconductivity and Hubbard physics on the same footing.