Large magnetothermopower and anomalous Nernst effect in HfTe5

Abstract

Topological quantum materials have stimulated growing attention because they reveal novel aspects of condensed matter physics and point to new opportunities in materials science, in particular for thermoelectrics. Here, we experimentally study thermoelectric effects in HfTe 5 , which was predicted to be at the boundary between strong and weak topological insulators. The magnetic field dependence of HfTe 5 thermoelectric properties attests to the anomalous character of this material, supported by our angle-resolved photoemission spectroscopy (ARPES) measurements. At 36 K, the thermopower of −277 μV/K is reached when a field of 0.4 Tesla is applied, while it is −157 μV/K at zero field and a large Nernst coefficient up to 600 μV/K is observed at 100 K with magnetic field of 4 T. A possible topologically nontrivial band structure is proposed to account for our observations. Our results constitute a highly constraining set of data for any model of transport based on HfTe 5 band structure. Furthermore, the extraordinary thermoelectric properties suggest a new paradigm for the development of thermoelectric applications based on layered transition-metal chalcogenides.

Spin‐Dependent Thermoelectric Transport in Cobalt‐Based Heusler Alloys

“…[ 92 ] Interestingly, in non‐magnetic Weyl and Dirac semimetal materials, it is easy to obtain an anomalous Nernst coefficient of more than 100 µV/K at low temperatures. [ 136–138 ] The origin of these large anomalous Nernst coefficients in non‐magnetic materials is a large Berry curvature evident in their electronic band structure. [ 109,139,140 ] Similarly, the intrinsic property of Berry curvature in ferromagnetic Weyl semimetals such as CMG is also believed to play a crucial role in obtaining large anomalous Nernst coefficients.…”

Enhancing Thermopower and Nernst Signal of High‐Mobility Dirac Carriers by Fermi Level Tuning in the Layered Magnet EuMnBi2

“…[27,28] In these materials, the high carrier mobility as well as low carrier density plays a vital role, since the conventional Nernst coefficient roughly tracks ω c τ/E F , [23,26] where ω c is the cyclotron frequency, τ the relaxation time, and E F the Fermi energy. In many of the Dirac/ Weyl semimetals, such a condition is well satisfied and hence the large Nernst effects were recently observed (e.g., in NbP, [29] Pb 1−x Sn x Se, [30] Cd 3 As 2 , [31,32] Ta(P,As), [33] and (Zr,Hf)Te 5 [34,35] ). In addition to the aforementioned conventional term, the anomalous term arising from the nonzero Berry curvature associated with the Dirac/Weyl points could also contribute to the Nernst signal (S yx ), when E F is located close to the Dirac/Weyl point.…”

“…In addition to the aforementioned conventional term, the anomalous term arising from the nonzero Berry curvature associated with the Dirac/Weyl points could also contribute to the Nernst signal (S yx ), when E F is located close to the Dirac/Weyl point. [36,37] The rapid increase in S yx at low fields was observed in some materials, [31][32][33][34][35] which is likely relevant to the anomalous term.…”

Anomalous Nernst Effect in Nonmagnetic Nodal Line Semimetal PbTaSe$_2$

“…We observed the step-like magnetic field dependence in the L phase, reminiscent of the anomalous Nernst effect in Dirac/Weyl semimetals reported in Refs. [32][33][34][35][36]. Furthermore, the temperature dependence of the Seebeck and Nernst coefficients shows the nontrivial peak structure probably associated with the linear band dispersion in the L phase (below 0.3 GPa).…”