Elementary excitation spectrum of one-dimensional electron systems in confined semiconductor structures: Zero magnetic field

We study theoretically the elementary excitation spectrum in various one-dimensional electron systems in the absence of a magnetic field. We first calculate the elementary excitations in a single quantum wire under the random-phase approximation. We find that the intersubband collective excitation frequency can be 5--6.5 times higher than the corresponding single-particle excitation energy due to a large depolarization shift. Next, we calculate the plasmon excitation energy of a double-layered quantum-wire system. Our result shows that the resonance peak splits due to the Coulomb interaction between electrons in different layers. We also study the elementary excitations in one-dimensional lateral quantum-wire superlattices. We include the Coulomb interaction between electrons in different wires and allow tunneling between neighboring wires. Finally, we calculate the spectral weights of the elementary excitations of both a single quantum wire and quantum-wire superlattices for various parameter values. We compare our results with recent experiments and find good agreement.