Thermoelectric Properties Of Silicene In The Topological- And Band-Insulator States

Thermoelectric effects in silicene nanoribbons are analyzed theoretically and numerically. The main focus is on the influence of topological edge states and transition between the topological-insulator and conventional gap-insulator states on the thermoelectric properties, and especially on the spin-related thermoelectric effects. The model includes a staggered exchange field and also an external electric field normal to the atomic plane. Both fields separately open a gap in the edge states and therefore lead to a nonzero thermopower in the vicinity of the gap edges. Interplay of both fields leads to a spin-dependent gap, and thus gives rise to a spin thermopower in addition to the conventional Seebeck effect. The role of the Coulomb interaction taken in the form of the Hubbard term in the mean-field approximation is also analyzed. This interaction leads to antiparallel configuration of the edge magnetic moments in the ground state. It is shown that the Coulomb interaction significantly modifies topological properties of the materials, and thus also their transport and thermoelectric properties.