Quantum theory of plasmons in lateral multiwire superlattices in the presence of subband quantization: Intersubband plasmons

We present a quantum theory of plasmons in lateral multiwire superlattices. The theory applies to lateral multiwire superlattices both with and without electron tunneling between wires. Special attention is paid to the strong-confinement case, where quantization effects are the most important and electron tunneling is weak. For a parabolic--confining-potential model, we find that the existence of an approximate sum rule results in an intersubband plasmon with energy shifted well beyond the subband-energy separation, and there are other intersubband plasmons with energies close to the subband-energy separation. Only the plasmon with the large energy shift creates a large electric dipole moment and thus couples strongly to the experimental probe. The coupling of intersubband plasmons to intrasubband plasmons is discussed.