  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 case 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.
