  We show electrical coherent manipulation of quadrupole-split nuclear spin
states in a GaAs/AlGaAs heterostructure on the basis of the breakdown of
quantum Hall effect. The electric quadrupole splitting in nuclear spin energy
levels is intentionally enhanced by applying an external stress to the
heterostructure. Nuclear magnetic resonance spectra with clearly separated
triple peaks are obtained, and Rabi oscillations are observed between the
nuclear spin energy levels. The decay of the spin-echo signal is compared
between the cases before and after the enhancement of quadrupole splitting.
