Discovery expected to lead to a whole new field of study

Researchers from Osaka University and the University of Tokyo have announced the discovery of a new magnet, which is capable of controlling Dirac fermions with zero mass.

It is expected this discovery will lead to a brand new field of study — strong correlated quantum transport of Dirac electrons — as well as major innovation in the area of super high-speed spintronics, which is the foundation for high-speed and energy-saving electronics.

This discovery came about following the successful creation of individual, high-quality EuMnBi2 crystals — a layered compound which is thought to have both properties of Dirac fermions and magnets — using flux growth in a high vacuum. 

What’s interesting about this material is that its architecture features two-dimensional layers of bismuth with Dirac electrons and europium with magnetic properties. To verify the correlation between Dirac fermions and the magnetic state, the team measured its electric resistance in a strong magnetic field; it recorded approximately 30-60 Tesla.

To reveal its magnetic state, the researchers conducted magnetic scattering experiments using synchrotron x-rays. They found that electric resistance changed depending on the magnetic order of europium. Additionally, it was found that when a magnetic field was applied perpendicularly to the 2D Bi layers and the direction of magnetic moment was rotated 90 degrees, the conductivity perpendicular to the layers was suppressed by 10% and the Dirac fermions were confined within each layer. This latter point is of particular importance — by confining the Dirac electrons in the 2D layer of Bi, the group observed a bulk half-integer quantum Hall effect (in which the value of the Hall resistance becomes discrete) in a bulk magnet of Dirac fermions for the first time ever. 

Due to its remarkable effectiveness, should this material prove scalable, it is expected to significantly advance the capabilities of high-speed and energy-saving electronics, as these technologies rely on the principles of spintronics, in which electron spin is manipulated to produce a desired outcome.

To learn more, read the full research report, entitled Quantum Hall effect in a bulk antiferromagnet EuMnBi2 with magnetically confined two-dimensional Dirac fermions.

Via Osaka University