Temperature-dependent Coulomb excitations in silicene

The temperature-dependent Coulomb screening and excitation spectrum of electrons in silicene are studied by the tight-binding model and the random-phase approximation. With the spin–orbit interaction, monolayer silicene is a narrow-gap semiconductor. At finite temperatures, the interplay between the intraband and interband transitions could lead to an undamped plasmon mode at low frequencies. The plasmon mode only exists in a limited region of temperature and momentum, corresponding to the constrained gap transition. Beyond that region, another damped plasmon mode dominates the excitation spectrum. The drastic change in the plasmon behavior might be observed experimentally, which could allow for the identification of the spin–orbit energy gap. (paper)