January 2021

Scientists at the U.S. Department of Energy's Ames Laboratory, along with collaborators at Brookhaven National Laboratory and the University of Alabama at Birmingham, have discovered a light-induced switch that twists the crystal lattice of the material, switching on a giant electron current that appears to be nearly dissipationless. The discovery was made in a category of topological materials that holds great promise for spintronics, topological effect transistors, and quantum computing.

Weyl and Dirac semimetals can host exotic, nearly dissipationless, electron conduction properties that take advantage of the unique state in the crystal lattice and electronic structure of the material that protects the electrons from doing so. These anomalous electron transport channels, protected by symmetry and topology, don't normally occur in conventional metals such as copper. After decades of being described only in the context of theoretical physics, there is growing interest in fabricating, exploring, refining, and controlling their topologically protected electronic properties for device applications. For example, wide-scale adoption of quantum computing requires building devices in which fragile quantum states are protected from impurities and noisy environments. One approach to achieve this is through the development of topological quantum computation, in which qubits are based on "symmetry-protected" dissipationless electric currents that are immune to noise.

Researchers at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Yale University have demonstrated the ability to control spin dynamics in magnetic materials by altering their thickness. The new study could lead to smaller, more energy-efficient electronic devices.

“Instead of searching for different materials that share the right frequencies, we can now alter the thickness of a single material—iron, in this case—to find a magnetic medium that will enable the transfer of information across a device,” said Brookhaven physicist and principal investigator Valentina Bisogni.

Researchers have recently demonstrated the long-range transport of magnetic hedgehogs, 3D topological spin structures that are often observed in common magnets. Their work could have important implications for the development of spintronic devices.

Nonlocal transport measurement of hedgehog currents in a three-dimensional insulating magnet. Image from article

Magnetic insulators are a class of materials widely used worldwide, mainly due to their ability to conduct electrical charges. Just like metals conduct electrical charges, magnetic insulators can conduct spins. Nonetheless, as spins are rarely conserved in materials and tend to disappear over long distances, so far, using magnetic insulators to achieve long-range transport has proved highly challenging.

Researchers at imec and Intel, led by PhD candidate Eline Raymenants, have created a spintronic logic device that can be fully controlled with electric current rather than magnetic fields. The Intel-imec team presented its work at the recent IEEE International Electron Devices Meeting (IEDM).

An electron’s spin generates a magnetic moment. When many electrons with identical spins are close together, their magnetic moments can align and join forces to form a larger magnetic field. Such a region is called a magnetic domain, and the boundaries between domains are called domain walls. A material can consist of many such domains and domain walls, assembled like a magnetized mosaic.

A research team, led by Dr. Kim Kyoung-Whan at the Center for Spintronics of the Korea Institute of Science and Technology (KIST), has proposed a new principle which could give a boost to spin memory devices.

Conventional memory devices are classified into volatile memories, such as RAM, that can read and write data quickly, and non-volatile memories, such as hard-disk, on which data are maintained even when the power is off. In recent years, related academic and industrial fields have been working to accelerate the development of next-generation memory that is fast and capable of maintaining data even when the power is off.

Researchers at the Czech Academy of Sciences, Charles University in Prague, ETH Zurich and other universities in Europe recently introduced a method to achieve the quenching of antiferromagnets into high resistivity states by applying either electrical or ultrashort optical pulses. This strategy could open interesting new avenues for the development of spintronic devices based on antiferromagnets.

Antiferromagnetism is a type of magnetism in which parallel but opposing spins occur spontaneously within a material. Antiferromagnets, materials that exhibit antiferromagnetism, have advantageous characteristics that make them particularly promising for fabricating spintronic devices. Due to their ultrafast nature, their insensitivity to external magnetic fields and their lack of magnetic stray fields, antiferromagnets could be particularly desirable for the development of spintronic devices. However, despite their advantages, most simple antiferromagnets have weak readout magnetoresistivity signals. Moreover, so far scientists have been unable to change the magnetic order of antiferromagnets using optical techniques, which could ultimately allow device engineers to exploit these materials' ultrafast nature.

University of Tokyo researchers have created a material that confines electrons in one dimension in the form of a special bismuth-based crystal known as a high-order topological insulator.

To create spintronic devices, new materials need to be designed that take advantage of quantum behaviors not seen in everyday life. For spintronic applications, a new kind of electronic material is required - a topological insulator. It differs from other materials by insulating throughout its bulk, but conducting only along its surface. And what it conducts is not the flow of electrons themselves, but a property of them known as their spin or angular momentum.