Large Magneto‐Transverse and Longitudinal Thermoelectric Effects in the Magnetic Weyl Semimetal TbPtBi

Abstract

Magnetic topological semimetals provide new opportunities for power generation and solid‐state cooling based on thermoelectric (TE) effect. The interplay between magnetism and nontrivial band topology prompts the magnetic topological semimetals to yield strong transverse TE effect, while the longitudinal TE performance is usually poor. Herein, it is demonstrated that the magnetic Weyl semimetal TbPtBi has high value for both transverse and longitudinal thermopower with large power factor (PF). At 300 K and 13.5 Tesla, the transverse thermopower and PF reach up to 214 µV K−1 and 35 µW cm−1 K−2, respectively, which are comparable to those of state‐of‐the‐art TE materials. Combining first‐principles calculations, longitudinal magnetoresistance and planar Hall resistance measurements, and two‐band model fitting, the large transverse thermopower and PF are attributed to both bipolar effect and large Hall angle. Moreover, the imperfectly compensated charge carriers and large transverse magnetoresistance induce the maximum magneto‐longitudinal thermopower of 251 µV K−1 with a PF of 24 µW cm−1 K−2 at 150 K and 13.5 Tesla, which is two times higher than that at zero magnetic field. This work demonstrates the great potential of topological semimetals for TEs and offers a new excellent candidate for magneto‐TEs.

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

“…S5, ESI†). Actually, this value is even higher than most single-crystalline thermomagnetic materials, such as single-crystalline Bi 97 Sb 3 , 10 Cd 3 As 2 , 16 ZrTe 5 , 17 PtSn 4 , 18 Mg 2 Pb, 19 and TbPtBi 28 (Fig. 1a and Fig.…”

“…Although the peak S yx of polycrystalline NbSb 2 is lower than the single-crystalline NbSb 2 , it is still much higher than most thermomagnetic materials reported before, such as 124 mV K À1 for polycrystalline NbP under 9 T at 140 K, 23 127 mV K À1 for polycrystalline Mg 3 Bi 2 under 13 T at 13.5 K, 24 125 mV K À1 for single-crystalline Cd 3 As 2 under 3 T at 350 K, 16 45 mV K À1 for single-crystalline PtSn 4 under 9 T at 10.3 K, 18 Fig. 2 200 mV K À1 for single-crystalline Mg 2 Pb under 10 T at 30 K, 19 and 225 mV K À1 for single-crystalline TbPtBi under 14 T at 240 K. 28 One main reason for the large S yx is originated from its unsaturated behavior under a high magnetic field. As shown in Fig.…”

“…The m e and m h of polycrystalline NbSb 2 are about 1.7 m 2 V À1 s À1 and 1.2 m 2 V À1 s À1 at 5 K, which are quite high values among those for the reported thermomagnetic materials, such as Cd 3 As 2 (m e = 6.5 m 2 V À1 s À1 , m h = 0.5 m 2 V À1 s À1 at 10 K) 16 , PtSn 4 (m e = 7.6 m 2 V À1 s À1 , m h = 7.6 m 2 V À1 s À1 at 10 K), 18 Mg 3 Bi 2 (m e = 0.48 m 2 V À1 s À1 , m h = 0.14 m 2 V À1 s À1 at 15 K), 24 and TbPtBi (m e = 0.3 m 2 V À1 s À1 , m h = 0.3 m 2 V À1 s À1 at 20 K). 28 Generally, it is considered that the polycrystals have lower carrier mobility than the single crystals due to the additional grain boundary scattering to carriers. Interestingly, herein the polycrystalline NbSb 2 have similar m e and m h with the single-crystalline NbSb 2 in the bc-plane.…”

“…Fig. 1 (a) Comparisons of the (a) Nernst power factor (PF) N and (b) Nernst figure-of-merit z N of polycrystalline NbSb 2 and some typical thermomagnetic materials reported before 10,[16][17][18][19][20][21][23][24][25][26][27][28]. The maximum (PF) N and z N of each thermomagnetic material are used in the figures.…”

New Recipe for Enhancing the Thermoelectric Performance in Topological Materials Carrying Single‐Pair Weyl Points Fermions and Phonons

“…Recently, the compensated charge carriers and giant magnetoresistance in magnetic WSM can be tuned to realize ultrahigh Nernst PF, as experimentally confirmed in WTe 2 , TbPtBi, BbP, etc. [46][47][48][49][50][51][52] Even if there are some reports of TE transport of WSMs, [53][54][55][56] connecting TE performance and the topology of Weyl points (WPs) is still not fully understood. It should be noted that while WPs were first introduced in the context of electrical systems, considerable efforts were thereafter made to apply them to spinless Bose systems, including phonon systems.…”