  Quantum mass acquisition, in which a massless (quasi)particle becomes massive
due to quantum corrections, is predicted to occur in several subfields of
physics. However, its experimental observation remains elusive since the
emergent energy gap is too small. We show that a spinor Bose-Einstein
condensate is an excellent candidate for the observation of such a peculiar
phenomenon as the energy gap turns out to be 2 orders of magnitude larger than
the zero-point energy. This extraordinarily large energy gap is a consequence
of the dynamical instability. The propagation velocity of the resultant massive
excitation mode is found to be decreased by the quantum corrections as opposed
to phonons.
