Phonon-drag thermopower and thermoelectric performance of MoS2 monolayer in quantizing magnetic field

Abstract

We present a theory of phonon-drag thermopower, , in MoS2 monolayer at a low-temperature regime in the presence of a quantizing magnetic field B. Our calculations for consider 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 dominate over other mechanisms. The is found to oscillate with the magnetic field where the lifting effect of the valley and spin degeneracies in MoS2 monolayer has been clearly observed. An enhanced with a peak value of mV K−1 at about T = 10 K is predicted, which is closer to the zero field experimental observation. In the Bloch–Grüneisen regime the temperature dependence of gives the power-law , where δ e varies marginally around 3 and 5 for unscreened and screened couplings, respectively. In addition, is smaller for larger electron density n e . The power factor PF is found to increase with temperature T, decrease with n e , and oscillate with B. The prediction of an increase of thermal conductivity with temperature and the magnetic field is responsible for the limit of the figure of merit (ZT). At a particular magnetic field and temperature, ZT can be maximized by optimizing electron density. By fixing cm−2, the highest ZT is found to be 0.57 at T = 5.8 K and B = 12.1 T. Our findings are compared with those in graphene and MoS2 for the zero-magnetic field.