Leveraging electron-phonon interaction to enhance the thermoelectric power factor in graphene-like semimetals

Electron-phonon interactions (EPIs) are presumably detrimental for thermoelectric performance in semiconductors because they limit carrier mobility. Here we show that enhanced EPIs with strong energy dependence offer an intrinsic pathway to a significant increase in the Seebeck coefficient and the thermoelectric power factor, particularly in the context of two-dimensional (2D) graphene-like Dirac bands. The increase is realized by enabling electron energy filtering through preferential scattering of electron/hole carriers. We prove this concept by implementing first-principles computational methods with explicit treatment of EPIs for a 2D gapless MoS2 allotrope, which has both massless Dirac bands and a heavy-fermion state that acts as the filter. We determine that the optimal location of the heavy state and hence the onset of the filtering process is at the Dirac point. Our study opens an avenue for attaining ultrahigh power factors via engineering the EPIs in graphene-like semimetals or identifying new compounds that intrinsically possess the featured electronic structure.