Phonon-drag thermopower and thermoelectric performance of MoSmonolayer in quantizing magnetic field.

We present a theory of phonon-drag thermopower,Sxxg, in MoSmonolayer at a low-temperature regime in the presence of a quantizing magnetic field. Our calculations forSxxgconsider the electron-acoustic phonon interaction via deformation potential (DP) and piezoelectric (PE) couplings for longitudinal (LA) and transverse (TA) phonon modes. The unscreened TA-DP is found to dominateSxxgover other mechanisms. TheSxxgis found to oscillate with the magnetic field where the lifting effect of the valley and spin degeneracies in MoSmonolayer has been clearly observed. An enhancedSxxgwith a peak value of∼1mV Kat about = 10 K is predicted, which is closer to the zero field experimental observation. In the Bloch-Grüneisen regime the temperature dependence ofSxxggives the power-lawSxxg∝Tδe, wherevaries marginally around 3 and 5 for unscreened and screened couplings, respectively. In addition,Sxxgis smaller for larger electron density. The power factor PF is found to increase with temperature, decrease with, and oscillate with. The prediction of an increase of thermal conductivity with temperature and the magnetic field is responsible for the limit of the figure of merit (). At a particular magnetic field and temperature,can be maximized by optimizing electron density. By fixingne=1012cm, the highestis found to be 0.57 at = 5.8 K and = 12.1 T. Our findings are compared with those in graphene and MoSfor the zero-magnetic field.