Magnetoplasmon excitations in quasi-two-dimensional Rashba spintronic systems: Oscillations, resonances, and energy gaps

Abstract

We report on the theoretical investigation of plasmon excitations in a quasi-two-dimensional electron gas (2DEG) in the presence of a perpendicular magnetic field and spin-orbit interaction induced by the Rashba effect. We derive and discuss the dispersion relations for charge-density excitations within the framework of Bohm-Pines' random-phase approximation. The magnetoplasmons in a 2DEG are known to be characterized by two important properties: (i) the oscillatory behavior of the dispersion curves in the short wavelength limit (SWL) and (ii) the resonance splitting at the frequency $\ensuremath{\omega}=n{\ensuremath{\omega}}_{c}$ in the long wavelength limit (LWL); $n\phantom{\rule{0.2em}{0ex}}(\ensuremath{\geqslant}2)$ being an integer and ${\ensuremath{\omega}}_{c}$ the cyclotron frequency. Here we study the effect of the Rashba spin-orbit interactions (SOIs) on these characteristics in depth. We observe that the SOI modifies drastically both the oscillatory behavior in the SWL and yields multiple resonance splittings [at $\ensuremath{\omega}=(n\ifmmode\pm\else\textpm\fi{}{x}_{0}){\ensuremath{\omega}}_{c}$] in the LWL. Such resonance splittings make the spintronic systems potential candidates for quantum-well-based new devices as spin filters. We discuss the dependence of the magnetoplasmon energy on the propagation vector, the magnetic field, the 2D charge-density, and the Rashba parameter characterizing the SOI.