Giant anomalous Nernst effect and quantum-critical scaling in a ferromagnetic semimetal

Akito Sakai, Yo Pierre Mizuta, Agustinus Agung Nugroho, Rombang Sihombing, Takashi Koretsune, Michi To Suzuki, Nayuta Takemori, Daisuke Rieko Ishii, Nishio Hamane, Ryotaro Arita, Pallab Goswami, Satoru Nakatsuji

Research output: Contribution to journalArticlepeer-review

Abstract

Inmetallic ferromagnets, the Berry curvature of underlying quasiparticles can cause an electric voltage perpendicular to both magnetization and an applied temperature gradient, a phenomenon called the anomalous Nernst effect (ANE)[1, 2]. Here, we report the observation of a giant ANE in the full-Heusler ferromagnet Co2MnGa, reaching Syx ∼-6 μV/K at room T, one order of magnitude larger than the maximum value reported for a magnetic conductor. With increasing temperature, the transverse thermoelectric conductivity or Peltier coefficient yx shows a crossover between T-linear and .T log(T) behaviors, indicating the violation of Mott formula at high temperatures. Our numerical and analytical calculations indicate that the proximity to a quantum Lifshitz transition between type-I and type-II magnetic Weyl fermions is responsible for the observed crossover properties and an enhanced αyx. The 2 T dependence of yx in experiments and numerical calculations can be understood in terms of a quantum critical scaling function predicted by the low energy effective theory over more than a decade of temperatures. Moreover, the observation of chiral anomaly or an unsaturated positive longitudinal magnetoconductance also provide evidence for the existence of Weyl fermions[10, 11] in Co2MnGa.

Original languageEnglish
JournalUnknown Journal
Publication statusPublished - 2018 Jul 12

ASJC Scopus subject areas

  • General

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