Doping as a tuning mechanism for magneto-thermoelectric effects to improve zT in polycrystalline NbP

Abstract: Weyl semimetals combine topological and semimetallic effects, making them candidates for interesting and effective thermoelectric transport properties. Here, we present experimental results on polycrystalline NbP, demonstrating the simultaneous existence of a large Nernst effect and a large magneto-Seebeck effect, which is typically not observed in a single material at the same temperature. We compare transport results from two polycrystalline samples of NbP with previously published work, observing a shift in the temperature at which the maximum Nernst and magneto-Seebeck thermopowers occur, while still maintaining thermopowers of similar magnitude. Theoretical modeling shows how doping strongly alters both the Seebeck and Nernst magneto-thermopowers by shifting the temperature-dependent chemical potential, and the corresponding calculations provide a consistent interpretation of our results. Thus, we offer doping as a tuning mechanism for shifting magneto-thermoelectric effects to temperatures appropriate for device applications, improving zT at desirable operating temperature. Furthermore, the simultaneous presence of both a large Nernst and magneto-Seebeck thermopower is uncommon and offers unique device advantages if the thermopowers are used additively. Here, we also propose a unique thermoelectric device which would collectively harness the large Nernst and magneto-Seebeck thermopowers to greatly enhance the output and zT of conventional thermoelectric devices.