Exactly Solvable Disorder-free Quantum Breakdown Model: Spectrum, Thermodynamics, and Dynamics

We introduce and study a disorder-free version of the quantum breakdown model with all-to-all interactions. The Hamiltonian factorizes into the product of the zero-momentum-mode occupation number and a quadratic Hamiltonian including only pairing terms. This structure makes the model exactly solvable and produces a large set of zero-energy states. We analyze its spectral, thermodynamic, and dynamical properties. In particular, we show how the factorized structure shapes the spectral form factor and the real-time dynamics. We also compute two-point functions and out-of-time-ordered correlators (OTOCs), and find a distinct early-time growth regime in the OTOCs. These results provide a solvable setting in which spectral properties and real-time dynamics can be analyzed in a controlled way in the absence of disorder, spatial structure, and environmental coupling.