The best of both worlds: Magnetism and Weyl’s semi-metals


The combination of magnetism and topology leads to new sciences and applications in thermoelectric, spintronics, photovoltaics, quantum computing and other quantum technologies Credit: MPI CPfS

Imagine a world where electricity could flow through the grid without any loss or where all of the world’s data could be stored in the cloud without the need for power plants. It seems unimaginable, but a path to such a dream has opened with the discovery of a new family of materials with magical properties.

These materials, Weyl’s magnetic semi-metals, are quantum in nature, but link the two worlds of topology and spintronics. Topological materials exhibit strange properties, including ultra-fast electrons which travel without any loss of energy. On the other hand, magnetic materials are essential in our daily life, from magnets for electric cars to spintronics devices in every hard drive of computers and in the cloud. The concept of a Weyl Magnetic Semi-Metal (WSM) was in the air but a real material has just been realized by Claudia Felser’s team, director at MPI CPfS, ​​Dresden, in two very different-Co2MnGa and Co3Sn2S2.

To find these extraordinary materials, Felser’s team scanned the materials database and compiled a list of promising candidates. The proof that these materials are magnetic WSMs has been obtained through studies of the electronic structure of Co2MnGa and Co3Sn2S2. Scientists from Claudia Felser’s group at MPI CPfS and from Stuart Parkin’s team at MPI of Microstructure Physics, Halle, in collaboration with Mr. Zahid Hasan’s team from Princeton, Yulin Chen’s team from University of ‘Oxford and the team of Haim Beidenkopf at the Weizmann Institute of Science, experimentally confirmed the existence of Weyl’s magnetic fermions in these two materials in studies published in three articles in Science today.

For the very first time, using angular resolution photoemission spectroscopy (ARPES) and scanning tunneling microscope (STM) experiments, time inversion symmetry shattered WSM states were observed, made possible by high quality single crystals grown at MPI CPfS. “The discovery of magnetic WSMs is a big step towards achieving high temperature quantum and spintronic effects. These two materials, which are members of the highly tunable Heusler and Shandite families, respectively, are ideal platforms for various future applications in spintronics and magneto – optical technologies for data storage and information processing as well as applications in energy conversion systems, ”says Stuart Parkin, Managing Director of the Max Planck Institute for Microstructural Physics, in Halle.

Magnetic topological states in Co2MnGa and Co3Sn2S2 play a crucial role in the origin of the observed abnormal quantum transport effects, due to the strong Berry curvature associated with their topological states. With the structures of nodal lines and bands of nodes of Weyl, Co2MnGa and Co3Sn2S2 are the only two currently known examples of materials which harbor both high anomalous Hall conductivity and an abnormal Hall angle. “Our materials exhibit the natural advantages of high order temperature, a clear topological band structure, low charge carrier density, and strong electromagnetic response. Designing a material that exhibits high temperature quantum abnormal Hall effect (QAHE) via quantum confinement of a WSM, and its integration into quantum devices is our next step, ”says Claudia Felser.

The discovery of magnetic WSMs is an important step towards achieving room temperature QAHE and forms the basis for new energy conversion concepts. Yan Sun immediately realized. Achieving QAHE at room temperature would be revolutionary in overcoming the limitations of many of today’s data-based technologies, which are affected by large power loss induced by electron scattering. This would pave the way for a new generation of low power consumption quantum and spintronic electronic devices.

The marriage of topology and magnetism in a Weyl system

More information:
Noam Morali et al, Fermi arc diversity on surface terminations of Weyl Co3Sn2S2 magnetic semi-metal, Science (2019). DOI: 10.1126 / science.aav2334

DF Liu et al. Semi-metallic magnetic Weyl phase in a Kagomé crystal, Science (2019). DOI: 10.1126 / science.aav2873

Ilya Belopolski et al. Discovery of the topological lines of Weyl’s fermions and the surface states of the drum skin in a magnet at room temperature, Science (2019). DOI: 10.1126 / science.aav2327

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Quote: Best of Both Worlds: Weyl’s Magnetism and Semi-Metals (September 20, 2019) retrieved September 27, 2021 from

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