Thomas Saunderson

Tuesday 3 Feb 2026, 14:00 → 15:00 Europe/London

S7.06

Symmetry as a Bridge Between Altermagnetism and Superconductivity

 

Tom G. Saunderson¹

1. Institute of Physics, Martin-Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany

 

Since the discovery of cuprate high-Tc superconductivity, numerous theoretical frameworks have been proposed to explain its mechanism. Anderson’s RVB picture [1] and U(1) gauge theory [2], to name a few, motivate a minimal one-band view that largely integrates out oxygen. By contrast, altermagnetism [3] yields a d-wave-like k-space magnetic texture arising from alternatingly rotated non-magnetic cages, with La₂CuO₄ (the parent compound of a high-T_c cuprate) serving as a prototypical example.

As a proof of principle, in this talk I will show that in La₂CuO₄ an alternating local pairing potential on the two Cu sublattices (±s(r)) produces a nodal, d-wave-like Δ(k). Since orthorhombic tilts are not the driving mechanism—and in fact suppress superconductivity in nickelates [4] - I instead show that the in-plane oxygen sublattice of CuO₂/NiO₂ layers, ubiquitous in cuprates and nickelates, intrinsically realises the same symmetry. Imposing an oxygen-centred, staggered s-wave pairing yields a d-wave gap with perfect C₄ symmetry, demonstrated self-consistently in NdNiO₂ from first principles. While the microscopic mechanism driving this form of order remains unclear, I provide speculation on its possible origin. Moreover, this description of superconductivity enables a direct mapping of a real-space superconducting order parameter onto a lattice-based picture, allowing superconductivity and Hubbard-model physics to be treated on the same footing.

 

[1] Science 235, 1196–1198 (1987).

[2] Physical Review Letters 76, 503–506 (1996).

[3] Physical Review X 12, 040501 (2022).

[4] Nature 621, 493 (2023).

[5] T. G. Saunderson et al, arXiv:2509.06814 (2025)