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, Rieko Ishii, Daisuke Nishio-Hamane, Ryotaro Arita, Pallab Goswami, Satoru Nakatsuji

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Abstract

In conducting ferromagnets, an anomalous Nernst effect—the generation of an electric voltage perpendicular to both the magnetization and an applied temperature gradient—can be driven by the nontrivial geometric structure, or Berry curvature, of the wavefunction of the electrons1,2. Here, we report the observation of a giant anomalous Nernst effect at room temperature in the full-Heusler ferromagnet Co2MnGa, an order of magnitude larger than the previous maximum value reported for a magnetic conductor3,4. Our numerical and analytical calculations indicate that the proximity to a quantum Lifshitz transition between type-I and type-II magnetic Weyl fermions5–7is responsible for the observed –Tlog(T) behaviour, with T denoting the temperature, and the enhanced value of the transverse thermoelectric conductivity. The temperature dependence of the thermoelectric response 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 an unsaturated positive longitudinal magnetoconductance, or chiral anomaly8–10, also provides evidence for the existence of Weyl fermions11,12in Co2MnGa.

Original languageEnglish
JournalNature Physics
DOIs
Publication statusAccepted/In press - Jan 1 2018
Externally publishedYes

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ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Sakai, A., Mizuta, Y. P., Nugroho, A. A., Sihombing, R., Koretsune, T., Suzuki, M. T., Takemori, N., Ishii, R., Nishio-Hamane, D., Arita, R., Goswami, P., & Nakatsuji, S. (Accepted/In press). Giant anomalous Nernst effect and quantum-critical scaling in a ferromagnetic semimetal. Nature Physics. https://doi.org/10.1038/s41567-018-0225-6