  We observe and study a special ground state of bosons with two spin states in
an optical lattice: the spin-Mott insulator, a state that consists of
repulsively bound pairs which is insulating for both spin and charge transport.
Because of the pairing gap created by the interaction anisotropy, it can be
prepared with low entropy and can serve as a starting point for adiabatic state
preparation. We find that the stability of the spin-Mott state depends on the
pairing energy, and observe two qualitatively different decay regimes, one of
which exhibits protection by the gap.
