Elementary excitations in one-dimensional quantum wires: Exact equivalence between the random-phase approximation and the Tomonaga-Luttinger model

We show---contrary to the viewpoint that the random-phase approximation (RPA) is progressively worse in lower dimensions---that the simple random-phase approximation provides an exact description for intrasubband plasmon dispersion in one-dimensional quantum wires, by establishing a general equivalence between the RPA and the strongly correlated Tomonaga-Luttinger model for the elementary-excitation spectra in one-dimensional Fermi systems. We also discuss the formal analogy between intrasubband and intersubband collective modes in quantum wires by showing that the one-dimensional intrasubband collective excitations can also be thought of as depolarization-shifted single-particle excitations. Our results explain why recent experimentally observed one-dimensional-plasmon dispersion in GaAs quantum wires can be quantitatively described by the RPA.