PLASMONS IN A SPATIALLY MODULATED QUASI-ONE-DIMENSIONAL QUANTUM-WIRE

We consider a quasi-one-dimensional superlattice consisting of a quant um wire, the equilibrium carrier density of which is spatially modulat ed along its length. We apply a simple hydrodynamic model for the coll ective excitations of low-dimensional inhomogeneous systems to calcula te the plasmon dispersion relation of the periodic heterostructure. As expected, the acoustic plasmon of the homogeneous quantum wire is fol ded into the first Brillouin zone due to the modulation and acquires o ptical branches. Gaps open at the zone boundary due to Bragg scatterin g, but unlike the two-dimensional and three-dimensional cases, no gap opens at the zone center for the modulated wire.