Massive spin collective mode in a quantum Hall ferromagnet

It is shown that the collective spin rotation of a single Skyrmion in a quantum Hall ferromagnet can be regarded as precession of the entire spin texture in the external magnetic field, with an effective moment of inertia which becomes infinite in the zero g-factor limit. This low-lying spin excitation may dramatically enhance the nuclear spin relaxation rate via the hyperfine interaction in the quantum well slightly away from filling factor ν=1.