Generalized Kramers-Wannier Self-Duality in Hopf-Ising Models

The Kramers-Wannier transformation of the 1+1d transverse-field Ising model exchanges the paramagnetic and ferromagnetic phases and, at criticality, manifests as a non-invertible symmetry. Extending such self-duality symmetries beyond gauging of abelian groups in tensor-product Hilbert spaces has, however, remained challenging. In this work, we construct a generalized 1+1d Ising model based on a finite-dimensional semisimple Hopf algebra H that enjoys an anomaly-free non-invertible symmetry Rep(H). We provide an intuitive diagrammatic formulation of both the Hamiltonian and the symmetry operators using a non-(co)commutative generalization of ZX-calculus built from Hopf-algebraic data. When H is self-dual, we further construct a generalized Kramers-Wannier duality operator that exchanges the paramagnetic and ferromagnetic phases and becomes a non-invertible symmetry at the self-dual point. This enlarged symmetry mixes with lattice translation and, in the infrared, flows to a weakly integral fusion category given by a mathbb{Z}₂ extension of Rep(H). Specializing to the Kac-Paljutkin algebra H₈, the smallest self-dual Hopf algebra beyond abelian group algebras, we numerically study the phase diagram and identify four of the six Rep\(H₈\)-symmetric gapped phases, separated by Ising critical lines and meeting at a multicritical point. We also realize all six Rep\(H₈\)-symmetric gapped phases on the lattice via the H-comodule algebra formalism, in agreement with the module-category classification of Rep\(H₈\). Our results provide a unified Hopf-algebraic framework for non-invertible symmetries, dualities, and the tensor product lattice models that realize them.