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arXiv · 2006.15769

Spin-polarized Weyl cones and gigantic anomalous Nernst effect in ferromagnetic Heusler films

Kazuki Sumida·Yuya Sakuraba·Keisuke Masuda·Takashi Kono·Masaaki Kakoki·Kazuki Goto·Weinan Zhou·Koji Miyamoto·Yoshio Miura·Taichi Okuda·Akio Kimura
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Abstract

Weyl semimetals are characterized by the presence of massless band dispersion in momentum space. When a Weyl semimetal meets magnetism, large anomalous transport properties emerge as a consequence of its topological nature. Here, using $in-situ$ spin- and angle-resolved photoelectron spectroscopy combined with $ab\ initio$ calculations, we visualize the spin-polarized Weyl cone and flat-band surface states of ferromagnetic Co$_2$MnGa films with full remanent magnetization. We demonstrate that the anomalous Hall and Nernst conductivities systematically grow when the magnetization-induced massive Weyl cone at a Lifshitz quantum critical point approaches the Fermi energy, until a high anomalous Nernst thermopower of $\sim 6.2$ $\rm \mu V K^{-1}$ is realized at room temperature. Given this topological quantum state and full remanent magnetization, Co$_2$MnGa films are promising for realizing high efficiency heat flux and magnetic field sensing devices operable at room temperature and zero-field.

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Kazuki Sumida, Yuya Sakuraba, Keisuke Masuda, Takashi Kono, Masaaki Kakoki, Kazuki Goto, Weinan Zhou, Koji Miyamoto, Yoshio Miura, Taichi Okuda, Akio Kimura. 2020-06-29. Spin-polarized Weyl cones and gigantic anomalous Nernst effect in ferromagnetic Heusler films. https://doi.org/10.1038/s43246-020-00088-w

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