Exploring the magnetoroton excitations in quantum wires: Inverse dielectric functions
A theoretical investigation has been made of the magnetoplasmon excitations in a quantum wire characterized by a confining harmonic potential and subjected to a perpendicular magnetic field. We study the (nonlocal, dynamic) inverse dielectric function to examine the charge-density excitations within a two-subband model in the framework of Bohm–Pines’ random-phase approximation. A particular stress is put on the (intersubband) magnetoroton excitation, which changes the sign of its group velocity twice before merging with the respective single-particle continuum. It has already been suggested that the electronic device based on such magnetoroton excitations can act as an active laser medium [see, e.g., M. S. Kushwaha, Phys. Rev. B 78, 153306 (2008)]. Scrutinizing the real and imaginary parts of the inverse dielectric function provides us with important information on the longitudinal and transverse (Hall) resistances of the system.