Manufacturing Bits: Sept. 24

Free flow electricity; Weyl fermions; papers galore.


Free flow electricity
Researchers have made some new breakthroughs in the emerging field of Weyl fermions and semi-metals, a move that could one day enable free flow electricity in systems.

In 2015, Princeton University and others finally proved a massless particle that had been theorized for 85 years–the Weyl fermion.

A fermion is a subatomic particle. Proposed by the mathematician and physicist Hermann Weyl in 1929, the Weyl fermion moves through a material and never collides with each other, according to the Paul Scherrer Institute (PSI). “These exotic particles, if applied to next-generation electronics, could allow for the nearly free and efficient flow of electricity, and thus greater power, in devices such as computers,” according to researchers from the U.S. Department of Energy and others.

In 2015, Princeton and others detected the Weyl fermion in a quasiparticle. This was located in synthetic crystals in a semi-metal called tantalum arsenide (TaAs).

So far, Weyl fermions have been found in select non-magnetic materials. Recently, though, PSI have found them in paramagnet materials. More specifically, these materials involve europium-cadmium-arsenic.

Researchers from PSI also manipulated the fermions with small magnetic fields, which in turn could pave the way to use them in the field of spintronics. Spintronics involves the study of intrinsic spin of the electron.

To measure the fermions, researchers used the Swiss Muon Source SμS. This is a tool, which examines the magnetic properties of materials. Researchers also visualized the fermions using X-ray spectroscopy.

“What we have proven here is that Weyl fermions can exist in a wider range of materials than previously thought,” said Junzhang Ma, a researcher at PSI.

“The difficult part,” said Ma, “was to identify a suitable magnetic material in which to look for these Weyl fermions.”

Weyl fermions
In a separate development, the Max Planck Institute for Chemical Physics of Solids have found magnetic Weyl semi-metals (WSM) in two compounds–Co2MnGa and Co3Sn2S2. Contributing to the research were Princeton, Oxford University and the Weizmann Institute of Science.

In this research, Weyl fermions were measured using angle-resolved photoemission spectroscopy (ARPES) and a scanning tunneling microscope (STM). “The discovery of magnetic WSMs is a big step towards the realization of high temperature quantum and spintronic effects. These two materials, that are members of the highly tunable Heusler and Shandite families, respectively, are ideal platforms for various future applications in spintronic and magneto-optic technologies for data storage, and information processing as well as applications in energy conversion systems,” said Stuart Parkin, the managing director of the Max Planck Institute of Microstructure Physics.

Claudia Felser, a researcher at the Max Planck Institute, added: “Our materials have the natural advantages of high order temperature, clear topological band structure, low charge carrier density, and strong electromagnetic response. The design of a material that exhibits a high temperature quantum anomalous Hall effect (QAHE) via quantum confinement of a magnetic WSM, and its integration into quantum devices is our next step.”

More fermions
The Hasan Group at Princeton has a Web page that is dedicated to Weyl fermions. Click here for more information on the subject. Click here too.

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