  Strong radial confinement in semiconductor nanowires leads to modified
electronic and phononic energy spectra. We analyze the current response to the
interplay between quantum confinement effects of the electron and phonon
systems in a gate-defined double quantum dot in a semiconductor nanowire. We
show that current spectroscopy of inelastic transitions between the two quantum
dots can be used as an experimental probe of the confined phonon environment.
The resulting discrete peak structure in the measurements is explained by
theoretical modeling of the confined phonon mode spectrum, where the
piezoelectric coupling is of crucial importance.
