Thermoelectric properties of topological Weyl semimetal family RAlX (R = La, Ce, Nd; X = Si, Ge): a first-principles investigation

Abstract

Weyl semimetals have emerged as an exciting class of materials with a myriad of non-trivial transport properties due to their topological nature. In this work, we investigate the thermoelectric properties of various experimentally reported members of a Weyl semimetal family RAlX for R = La, Ce and Nd and X = Si and Ge using first-principles calculations within the semi-classical Boltzmann transport theory. Our comprehensive analysis of the electronic structure and phonon dispersion sheds light on various aspects of thermoelectric transport in this family of materials. Our calculations show that the transport in RAlX is dominated by the d-orbitals of R and the p-orbitals of Al and X. We also discover that the phonon contribution to the thermal conductivity is much smaller compared to the electronic contribution, a desirable factor for thermoelectrics. We report the highest value of thermoelectric figure of merit zT = 0.56 for CeAlGe at 900 K, which is encouraging when compared among semimetals. Our work reveals that the combination of topologically non-trivial Weyl dispersion and the presence of heavy elements in the RAlX family offers a promising avenue for thermoelectric applications in Weyl semimetals and therefore makes multifunctional applications possible.