Higher-spin Richardson-Gaudin model with time-dependent coupling Exact dynamics

We determine the exact asymptotic many-body wave function of a spin-s Richardson-Gaudin model witha coupling inversely proportional to time, for time evolution starting from the ground state at t = 0⁺ and forarbitrary s. Contrary to common belief, the resulting wave function cannot be derived from the spin-1/2 caseby merging spins, but instead requires independent treatment for each spin size. The steady state is nonthermaland, in contrast to the spin-1/2 case, does not conform to a natural Generalized Gibbs Ensemble. We show thatmean-field theory is exact for any product of a finite number of spin operators on different sites. We discuss howthese findings can be probed in cavity QED and trapped ion experiments.