Light-Induced Switchable Odd-Parity Altermagnetism in One- and Two-Dimensional Triangulene Crystals

The recent emergence of altermagnetism has enriched the classification of magnetic states. The symmetry constrained even-parity and odd-parity altermagnets are mainly limited to collinear and noncollinear spins in two- and three-dimensional materials. In this work, guided by the symmetry classification, we propose a general strategy for designing unconventional p-wave altermagnets in one-dimensional (1D) collinear antiferromagnets with the switchable spin-splitting under circularly polarized light, also extendable to the odd-parity altermagnets in two-dimensional (2D) collinear antiferromagnets. First-principles calculations on experimentally synthesized 1D and 2D triangulene crystals further validate our design principles, realizing the extrinsic p-wave and f-wave altermagnets. By coupling 2D altermagnetic triangulene crystals to s-wave superconductors, the high-Chern-number topological superconductivity can be achieved within spin-splitting energy windows. Our work introduces a new mechanism to engineer light-induced 1D and 2D odd-parity altermagnets and provides a molecular platform to explore the metal-free altermagnetism in π-conjugated covalent organic frameworks.