One-dimensional plasmons in magnetic fields

We have investigated the wave-vector $\mathrm{}\left(q\right)\mathrm{}$ and magnetic-field $\mathrm{}\left(B\right)\mathrm{}$ dependence of plasmons propagating along quantum wires by means of resonant Raman spectroscopy. We observe a mode with a well-pronounced negative $B$ dispersion that arises from the skipping-orbit motion of the individual electrons within the collective excitation. At higher frequencies we find a set of additional modes that represent a superposition of freely propagating oscillations along the wire and confined oscillations perpendicular to the wires. These modes exhibit in a magnetic field a strong interaction with harmonics, $n=2,3\mathrm{}\dots$, of the cyclotron frequency $n{\omega }_c.$