Enhancement of the thermoelectric power factor in monolayer PbBiI: staggered exchange field effect

Abstract

The unique features of the monolayer PbBiI originate from the gapped and gapless states protected by the time-reversal symmetry. These states appear with the angular momenta J = {1/2, 3/2}. The engineering of thermoelectric performance in monolayer PbBiI is highly desirable due to the forbidden backscattering mechanism of electrons. Herein, a known physical staggered exchange field is implemented to calculate the Onsager transport coefficients within the Kubo–Greenwood framework. This, in turn, enhances the power factor (PF) through highly dispersive and degenerate energy bands resulting from the staggered exchange field. We report exceptional 133%, 53%, and 22% enhancements of PF at temperatures 480 K, 460 K, and 440 K, respectively, when we turn on the exchange field to act on J = 3/2, J = 1/2, and both Js. The predicted PFs propose a new research line to achieve the highest thermoelectric efficiency in low-dimensional materials.