Non-invertible Symmetry Breaking in a Frustration-Free Spin Chain
摘要
A nearest-neighbor, frustration-free spin \(\frac{1}{2}\) chain can be constructed via projectors of various ranks á la Bravyi-Gosset. We show that in the rank 1 case this system is gapped and has two ground states resembling ferromagnetic states. These states spontaneously break the non-invertible symmetry connecting them. The latter is proved using the machinery of algebraic quantum theory. The non-invertible symmetries of this system do not come from a duality.