Spin polarized edge states in TlGaS2 nanoribbons

We have investigated TlGaS2 single-layer and TlGaS2 nanoribbons using density functional theory (DFT). Phonon dispersion curves calculated within the density functional perturbation theory indicate that the TlGaS2 single-layer is dynamically stable. Starting from optimized TlGaS2 single-layers, unterminated and terminated ribbon morphologies with varying edge Tl coverages were constructed. In order to account for the weak interaction between Tl and S atoms, van der Waals correction to DFT was employed. The electronic and magnetic structures of TlGaS2 ribbons are modulated by the edge morphology. Dangling bond, non-bonding, and free-electron-like edge states are formed. The ribbons have metallic conduction channels stemming from parabolic bands crossing the Fermi level. The edge states appearing in the fundamental energy gap induce spin polarization at the edges. The TlGaS2 nanoribbons provide two magnetic conduction channels along the Tl chains, and thus the nanoribbon acts as two magnetic nanowires.