Thermoelectric and thermomagnetic transport in triple-point topological metal Molybdenum Phosphide (MoP)*

MoP is a topological metal which had been shown to host a triple point fermion in its band structure with a Weyl point in the bulk bands [1]. This complex band structure is a strong motivation for studying electrical and thermal transport. Single-crystalline MoP previously demonstrated an extremely high electrical conductivity and the potential for hydrodynamic charge flow [2]. In this work, both the Seebeck effect and Nernst effect are investigated for the first time in polycrystalline MoP samples. Additionally, thermal conductivity, electrical resistivity, heat capacity, and the Hall effect are determined as functions of grain size, temperature, and magnetic field. Compared to single-crystalline MoP [2], both thermal and electrical conductivity are found to be 1-2 orders of magnitude smaller in polycrystalline samples. From Wiedemann-Franz law analysis, electronic and phonon thermal conductivity are determined, and the former is found to be dominating at higher temperatures. This is contrary to the single-crystalline MoP, due to more scattering of phonons. Other transport properties show typical metallic behavior with relatively small Seebeck and Nernst effects due to a large charge carrier density.

[1] B. Q. Lv et al. Nature 546 (2017).

[2] N. Kumar et al. Nat. Commun 10 (2019).