Abstract

We present systematic theoretical results on thermal and thermoelectric transport properties in semimetals based on the variational method of the linearized Boltzmann equation. Momentum-conserving inelastic electron-hole scattering is known to play an important role in the unusual transport of semimetals, including the broad T^2 temperature dependence of the electrical resistivity and the strong violation of the Wiedemann-Franz law. By treating the electron-hole scattering more precisely beyond the relaxation time approximation, we discuss the behaviors of the transport coefficient. It is found that deviations from the compensation condition significantly increase the Seebeck coefficient, along with crucial suppressions of the Lorenz ratio, which quantifies the WF law. The result indicates that uncompensated semimetals with the electron-hole scattering have high thermoelectric efficiency when the phonon contribution to thermal conductivity is suppressed.