Spin-Valley Optical Selection Rule and Strong Circular Dichroism in Silicene

Abstract

Silicene (a monolayer of silicon atoms) is a topological insulator, which undergoes a topological phase transition to a band insulator under an external electric field. The spin polarization is unique and opposite at the K and K' points due to the spin-orbit coupling. Accordingly, silicene exhibits a strong circular dichroism with respect to optical absorption, obeying a certain spin-valley selection rule. It is remarkable that this selection rule is drastically different between these two types of insulators owing to a band inversion taking place at the phase transition point. Hence we can tell experimentally whether silicene is in the topological or band insulator phase by circular dichroism. Furthermore the selection rule enables us to excite electrons with definite spin and valley indices by optical absorption. Photo-induced current is spin polarized, where the spin direction is different between the topological and band insulators. It is useful for future spintronics applications.

4 pages, 7 figures

References in corpus (4)

• Valley Dependent Optoelectronics from Inversion Symmetry Breaking
• Intrinsic and Rashba Spin-orbit Interactions in Graphene Sheets
• Valley-Polarized Metals and Quantum Anomalous Hall Effect in Silicene
• Quasi-Topological Insulator and Trigonal Warping in Gated Bilayer Silicene

Cited by in corpus (4)

• Photo-Induced Topological Phase Transition and a Single Dirac-Cone State in Silicene
• Spin-Valleytronics in Silicene: Quantum-Spin-Quantum-Anomalous Hall Insulators and Single-Valley Semimetals
• Optical Signatures of the Tunable Band Gap and Valley-Spin Coupling in Silicene
• Hexagonally Warped Dirac Cones and Topological Phase Transition in Silicene Superstructure