Motivated by the recent experimental realization of synthetic gauge fields in ultracold atoms, we investigate one-dimensional attractive Fermi gases with a time-dependent gauge flux on the spin sector. By combining the methods of the Bethe ansatz with complex twists and Landau-Dykhne, it is shown that a spin-depairing transition occurs, which may represent a nonequilibrium transition from fermionic superfluids to normal states with spin currents caused by a many-body quantum tunneling. For the

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... ase of the Hubbard ring at half filling, our finding forms a dual concept with the dielectric breakdown of the Mott insulator discussed in Phys. Rev. B 81, 033103 (2010). We analyze cases of arbitrary filling and continuum model, and show how the filling affects the transition probability.