Thermal transport in Weyl semimetal BaMnSb₂: a first-principles study

Orthorhombic BaMnSb₂ is a topological semimetal consisting of alternative stacking of Sb, Ba, and MnSb layers. A recent experiment revealed a low thermal conductivity and a modest thermal power of BaMnSb₂, suggesting that BaMnSb₂ could be a promising thermoelectric material. Employing density functional theory, we perform an in-depth investigation of the electronic structure, phononic structure, and thermal transport of BaMnSb₂, addressing the effect of Coulomb repulsion and spin-orbit coupling. We find that the phonon band structure of BaMnSb₂ is insensitive to the Coulomb repulsion, spin-orbit coupling, and even long-range magnetic ordering. Assessing the three-phonon scattering, a low and highly anisotropic lattice-mediated thermal conductivity of BaMnSb₂ is observed from our calculations. Thermal power is also calculated by the semiclassical Boltzmann theory with a constant relaxation time approximation. Avenues to enhance the thermal power and lower the thermal conductivity of BaMnSb₂ will be discussed including doping and mechanical strain.