Phonon-induced conductivity of ballistic quantum wires

We have used pulses of nonequilibrium phonons to probe the electron-phonon interaction in a ballistic quantum wire. Phonons incident on the wire caused a decrease in its conductance, $-\Delta G,$ due to phonon-induced electron backscattering. We observed giant oscillations in $-\Delta G$ as the wire was narrowed. Maxima occurred when $E_F$ was close to the bottom of any one-dimensional subband. An applied magnetic field broadened and shifted the phonoconductivity oscillations, due to the depopulation of the hybrid electric-magnetic subbands. When the wire was just pinched off, the phonons caused a strong increase in the conductivity due to phonon-assisted transfer of electrons across the potential barrier.