Collective excitations in quasi-one-dimensional Rashba spintronic systems: Zero magnetic field

We report on the theoretical investigation of plasmon excitations in a quasi-one-dimensional

electron gas (Q-1DEG) in the presence of spin-orbit (SO) interaction induced by Rashba effect.

Our model consists of a lateral parabolic confinement and the interface-induced (Rashba)

electric field transverse to the original 2DEG. We derive and discuss the dispersion relations

for both intra- and inter-subband excitations within the framework of the random-phase

approximation (RPA). The zero-field spin splitting is observed to modify both the single-particle

as well as the collective excitations of the system. The resultant mechanism gives rise to a pair

of collective and single-particle excitations with significant energy splitting between the

respective modes of excitation within the two-subband model. It is observed that at least two

plasmon modes remain free from Landau damping until a considerably higher value of the propagation

vector. Depending upon the material parameters these plasmons may occur in the terahertz frequency

range. As such, the electron spin dynamics of Q1DEG can be of potential interest in the

quantum-wire-based new devices in the terahertz frequency range. We discuss the dependence of the

plasmon energy on the Rashba parameter, the one-dimensional charge density, and the propagation

vector.