  We report the observation of multiple harmonic generation in electric dipole
spin resonance in an InAs nanowire double quantum dot. The harmonics display a
remarkable detuning dependence: near the interdot charge transition as many as
eight harmonics are observed, while at large detunings we only observe the
fundamental spin resonance condition. The detuning dependence indicates that
the observed harmonics may be due to Landau-Zener transition dynamics at
anticrossings in the energy level spectrum.
