An integrable spin chain with Hilbert space fragmentation and solvable real time dynamics

Understand

We revisit the so-called folded XXZ model, which was treated earlier by two independent research groups.

• We argue that this spin-1/2 chain is one of the simplest quantum integrable models, yet it has quite remarkable physical properties.
• The particles have constant scattering lengths, which leads to a simple treatment of the exact spectrum and the dynamics of the system.
• The Hilbert space of the model is fragmented, leading to exponentially large degeneracies in the spectrum, such that the exponent depends on the particle content of a given state.