Abstract
We study the optical absorption properties of silicene and germanene in the presence of the perpendicular magnetic and electric fields. Their low-energy Landau level (LL) spectra are controllable by an external electric field, where the spin- and valley-degeneracy of the LLs are strongly influenced by the electric and Zeeman fields. The electric field has removed spin-degeneracy at a given valley. Analytical expressions for the magneto-optical absorption coefficient (MOAC) are expressed in the presence of the interaction between carriers and random impurities and the intrinsic phonons including the spin and valley effects. The results evaluated for the topological insulator and valley-spin-polarized metal phases showed that when the electric field is included, the MOAC peaks are separated for opposite spin cases where the splitting in germanene is stronger than that in silicene. The peak's intensity caused by the carrier-photon-impurity scattering is the highest, the next is the carrier-photon scattering, while the carrier-photon-phonon scattering shows the lowest in both materials. Among the different phonon modes, the out-of-plane (ZA) mode in silicene dominates the others, being attributed to its buckled atomic structure, which does not exist in graphene. When the ZA mode is taken into account, the estimated resultant mobility from the full-width at half-maximum is significantly supported by the experimental result in silicene.
Highlights
Besides graphene [1], one of the most widely studied twodimensional (2D) materials, recently silicene and germanene, the other 2D group-IV materials, have attracted great interest for their extraordinary properties [2,3]
The results evaluated for the topological insulator and valley-spin-polarized metal phases showed that when the electric field is included, the magneto-optical absorption coefficient (MOAC) peaks are separated for opposite spin cases where the splitting in germanene is stronger than that in silicene
While z = 0 stands for the case of without electric field, the latter are chosen to present the two special phases of silicene and germanene: the case of z = 0.5λSO refers to the topological insulator (TI) phase while the case of z = λSO is for the valley-spin-polarized metal (VSPM) phase [46]
Summary
Besides graphene [1], one of the most widely studied twodimensional (2D) materials, recently silicene and germanene, the other 2D group-IV materials, have attracted great interest for their extraordinary properties [2,3]. The spin Hall effect in these two novel materials is stronger than that in graphene [7,8,9] Another important characteristic of silicene comes from its buckled structure, which allows us to control its properties by an electric field [10], exchange field [11], or the circular polarized radiation [12]. The magneto-optical absorption is one of the important properties studied in the literature in bulk semiconductors [24], low-dimensional systems [25,26,27], and more recently in monolayers of graphene [28] and transition-metal dichalcogenides (TMDCs) [29,30,31] In this phenomenon, in quantizing magnetic field, optical absorption takes place by absorbing a photon and making inter-Landau level transition with/without the assistance of impurity or phonons scattering.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
