Thermoelectric and thermal properties of the weakly disordered non-Fermi liquid phase of Luttinger semimetals

Abstract

We compute the thermoelectric and thermal transport in the weakly disordered non-Fermi liquid phase of the Luttinger semimetals at zero doping, where the decay rate associated with the (strong) Coulomb interactions is much larger than the electron-impurity scattering rate. To this end, we implement the Mori-Zwanzig memory matrix method, that does not rely on the existence of long-lived quasiparticles in the system. We find that the thermal conductivity at zero electric field scales as $\bar{\kappa}\sim T^{-n}$ (with $0\lesssim n\lesssim 1)$ at low temperatures, whereas the thermoelectric coefficient has the temperature dependence given by $\alpha\sim T^{p}$ (with $1/2\lesssim p\lesssim 3/2)$. These unconventional properties turn out to be key signatures of this long sought-after non-Fermi liquid state in the Luttinger semimetals, which is expected to emerge in strongly correlated spin-orbit coupled materials like the pyrochlore iridates. Finally, our results indicate that these materials might be good candidates for achieving high figure of merit for thermoelectric applications.