Abstract

This paper presents a theoretical investigation of the plasmon excitation spectrum in monolayer silicene systems at finite temperatures under the random-phase approximation. Because of silicene's buckled honeycomb structure and strong spin–orbit coupling (△so), its bandgap can be tuned electrically via an external perpendicular field that induces a sublattice potential difference (△z). This study examines how temperature and △z influence plasmon dispersion, damping, and stability. The results show that the plasmon mode maintains its characteristic pq dependence on the wave vector at long wavelengths but undergoes a pronounced redshift and enhanced Landau damping as the temperature increases, particularly near the critical condition △z ≈ △so, where the electronic gap closes and the single-particle excitation region expands. When the gap reopens, the undamped plasmon region is restored, and the mode becomes more stable. Moreover, the plasmon frequency depends nonmonotonically on temperature, decreasing at intermediate temperatures and increasing again at higher values as a result of thermal carrier activation. These findings demonstrate the importance of thermal and electric-field effects in determining the plasmonic behavior of silicene and could inform the design of stable, tunable plasmonic and optoelectronic devices based on two-dimensional silicon.