Weyl Semimetal States Generated Extraordinary Quasi‐Linear Magnetoresistance and Nernst Thermoelectric Power Factor in Polycrystalline NbP

Abstract

Unsaturated and extremely large magnetoresistance (MR), as well as the giant Nernst effect, are intriguing transport phenomena in Weyl semimetals, which are technically appealing for potential applications in magneto-electric sensors and transverse thermoelectric conversion. The prominent properties are originated from Weyl semimetal states, i.e., the coexistence of electron and hole pockets combined with linear band dispersion. However, previous studies have been focused on small-sized single crystals, rendering the practical applications of Weyl semimetals. Here, it is reported an unsaturated, quasi-linear MR as well as a very large Nernst power factor PF xy in the prepared centimeter-sized and polycrystalline Weyl semimetal NbP. An extraordinary MR of ≈2 × 10 4 % is observed below 60 K with a magnetic field up to 55 T and persists to elevated temperatures. The unusual quasi-linear MR behavior is explained by the theory of classical linear MR arising from structural disorder. The polycrystalline NbP exhibits state-of-the-art PF xy that reaches a maximum value of 74.81 μW cm -1 K -2 at 9 T and 220 K, which is 1.5 times larger than its longitudinal thermoelectric power factor PF xx . Given that polycrystalline Weyl semimetal, NbP is suitable for large-scale production, the results pave the way for its practical applications in magneto-electric sensors and transverse thermoelectric conversion.

Giant transverse thermoelectric effect induced by topological transition in polycrystalline Dirac semimetal Mg3Bi2

“…In our investigated range (0-14 Tesla), the as-fabricated Mg 3+d Bi 2 :Mn 0.1 showed a maximum value of 20 393 mW m À1 K À2 under a 6 Tesla magnetic field, which was almost an order of magnitude higher than the 2182 mW m À1 K À2 value reported for the Mg 3+d Bi 2 sample. 19 This value was also much higher than that of all polycrystalline materials and most single-crystal materials reported to date, including the Dirac semimetals ZrTe 5 , PtSn 4 , 11 Pb 0.77 Sb 0.23 Se, 20 Cd 3 As 2 , 8 and NbP; 10,13,14,26 the semimetals Mg 2 Pb 21 and Bi 77 Sb 23 ; 22 and the narrow-band semiconductors Ag 2(1+x) Se 23 and Re 4 Si 7 . 24 We also note that this value is still lower than that for the single-crystal Weyl semimetal WTe 2 .…”

A giant Nernst power factor and figure-of-merit in polycrystalline NbSb2 for Ettingshausen refrigeration

“…However, currently the investigation on polycrystalline thermomagnetic materials is very rare. [22][23][24][25] Particularly, as shown in Fig. 1, the (PF) N and z N of the reported polycrystalline thermomagnetic materials are much lower than those of single-crystalline thermomagnetic materials.…”

Magnetism Modulation for Cryogenic Thermoelectric Enhancements in Fe3O4 Nanoparticle-Incorporated Bi0.85Sb0.15 Nanocomposites

“…The apparent nonlinear relation of Hall resistivity (ρ xy ) vs H indicates that both electrons and holes play important roles in the electronic transport of the composites (Figure S5). Therefore, the electron ( n e ) and hole ( n h ) concentrations and their mobility (μ e , μ h ) are derived from electrical conductivity under a magnetic field based on the semiclassical two-band model (eqs S1–S3). The temperature dependence of the carrier concentration is shown in Figure a.…”

“…In recent years, a few emerging studies are focused on the effect of the external magnetic field and incorporation of magnetic nanoparticles on the TE properties of materials . The significant improvement of S and ZT values under the transverse magnetic field has been observed in some semimetals and semiconductors, such as Cd 3 As 2 , NbP, and Bi–Sb, , which can be attributed to the modulation of the magnetic field to carrier scattering and electronic density of states . Meanwhile, the magnetism introduced by magnetic nanoparticles (Fe, , Co, Ni, and Fe 3 O 4 , ) can regulate the electronic and thermal transport properties synergistically in the (Bi,Sb) 2 (Te,Se) 3 , ,, CoSb 3 -based, , or half-Heusler TE materials.…”