Bipolarity of large anomalous Nernst effect in Weyl magnet-based alloy films

• Published in: Nature physics 2024-02, Vol.20 (2), p.254-260
• Main Authors: Noguchi, Shun, Fujiwara, Kohei, Yanagi, Yuki, Suzuki, Michi-To, Hirai, Takamasa, Seki, Takeshi, Uchida, Ken-ichi, Tsukazaki, Atsushi
• Format: Article
• Language: English
• Subjects: 639/4077/4107; 639/766/1130/2798; 639/766/119/1001; 639/766/119/2792; 639/766/119/997; Atomic; Bipolarity; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Electric potential; Electromagnetism; Energy; Energy conversion; Ferromagnetism; Magnetic fields; Magnets; Mathematical and Computational Physics; Molecular; Nernst-Ettingshausen effect; Nickel; Optical and Plasma Physics; Physics; Physics and Astronomy; Theoretical; Thermal energy; Thermoelectricity; Thermopiles; Thin films; Topology; Voltage
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-023-02293-z

A thermopile device converts thermal energy to electrical energy. Controlling the polarity of the thermoelectric voltage that such a device generates is an important part of enhancing its thermoelectric output. Constructing thermopile devices where the mechanism is based on the anomalous Nernst effect in topological magnets and where one can control the bipolarity is still hard to do. Here we demonstrate the bipolarity of a large anomalous Nernst effect in a series of Weyl ferromagnet Co 3 Sn 2 S 2 -based alloy films by tuning the Fermi energy. We illustrate the bipolarity of the anomalous Nernst signal originating from the intrinsic Berry curvature contribution by systematically regulating the Fermi energy by nickel or indium substitution while maintaining a topological band feature of the Weyl ferromagnet. The bipolarity enables the construction of the Weyl magnet-based anomalous Nernst thermopile that generates large thermoelectric output at zero magnetic field. These demonstrations of bipolar large anomalous Nernst effect in Co 3 Sn 2 S 2 -based films will stimulate the device development of efficient thermoelectric energy conversion exploiting topological magnets. The key to enhance the output of a thermoelectric device is to be able to regulate the thermoelectric voltage generation. Topological magnet Co 3 Sn 2 S 2 -based devices show the way to achieve that goal.