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 cause d a decrease in its conductance, -Delta G, due to phonon-induced electron b ackscattering. We observed giant oscillations in -Delta G as the wire was n arrowed. Maxima occurred when E-F was close to the bottom of any one-dimens ional subband. An applied magnetic field broadened and shifted the phonocon ductivity oscillations, due to the depopulation of the hybrid electric-magn etic subbands. When the wire was just pinched off, the phonons caused a str ong increase in the conductivity due to phonon-assisted transfer of electro ns across the potential barrier.