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Discovery of Giant, Non-saturating Thermopower in Topological Semimetal at Quantum Limit

Authors
  • Han, Fei
  • Andrejevic, Nina
  • Nguyen, Thanh
  • Kozii, Vladyslav
  • Nguyen, Quynh
  • Ding, Zhiwei
  • Pablo-Pedro, Ricardo
  • Parjan, Shreya
  • Skinner, Brian
  • Alatas, Ahmet
  • Alp, Ercan
  • Chi, Songxue
  • Fernandez-Baca, Jaime
  • Huang, Shengxi
  • Fu, Liang
  • Li, Mingda
Publication Date
Nov 13, 2019
Source
eScholarship - University of California
Keywords
License
Unknown
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Abstract

Thermoelectrics are promising by directly generating electricity from waste heat. However, (sub-) room-temperature thermoelectrics have been a long-standing challenge, due to the vanishing electronic entropy at low temperature. Topological materials offer a new avenue for energy harvesting applications. Recent theories predicted that topological Weyl semimetals (WSMs) at the quantum limit can lead to a non-saturating longitudinal thermopower, as well as a quantized thermoelectric Hall conductivity approaching to a universal value. Here, we experimentally demonstrate the non-saturating thermopower and the signature of quantized thermoelectric Hall conductivity in WSM tantalum phosphide (TaP). An ultrahigh longitudinal thermopower Sxx = 1.1x10^3 muV/K, along with a power factor ~500 muW/cm/K^2, are observed ~40K. Moreover, the thermoelectric Hall conductivity develops a plateau at high-fields and low temperatures, which further collapses onto a single curve determined by universal constants. Our work highlights the unique WSM electronic structure and topological protection of Weyl nodes toward low-temperature energy harvesting applications.

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