Light-induced twisting of Weyl nodes switches on giant electron current

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 find that thickness of magnetic materials can help control their spin dynamics

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 study the long-range transport of magnetic hedgehogs

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 imageNonlocal 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.

University of Tokyo team creates a higher-order topological insulator

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.

Researchers show how to transmit high frequency alternating spin currents using antiferromagnetic spintronics devices

Researchers from Exeter University, in collaboration with the Universities of Oxford, California Berkeley, and the Advanced and Diamond Light Source have experimentally demonstrated that high frequency alternating spin currents can be transmitted by, and sometimes amplified within, thin layers of antiferromagnetic NiO.

The researchers say that these results demonstrate that the spin current in thin NiO layers is mediated by evanescent spin waves, a mechanism akin to quantum mechanical tunnelling. This could lead to more efficient future wireless communication technology based on such antiferromagnetic spintronics devices.

Researchers develop a way to inject an ultra-fast pulse of spin current

Researchers NTU, NUS, A*STAR and the Los Alamos National Lab have demonstrated that it is possible to inject an ultra-short pulse of spin current (less than a picosecond) from a metal to a semiconductor in a very efficient way.

Ultra-short laser pulses on cobalt - spin polarization photo

The researchers used a short laser pulse on cobalt (a magnetic material) - which generated a spin-polarized "swarm" of excited electrons. The spin-polarized electrons travel outside of the material - into adjacent materials. This creates an extremely efficient spin injection.

Perovskites are promising as spintronic materials, researchers develop two new perovskite spintronics devices

Researchers from the University of Utah developed two spintronics devices based on perovskite materials. The researchers use these new devices to demonstrate the high potential of perovksites for spintronics systems. This is a followup to the exciting results announced in 2017 by the same group that showed advantages of perovskites for spintronics.

Perovskite spintronics LED wavelength (Utah University)

The researchers use an organic-inorganic hybrid perovskite material that has a heavy lead atom that features strong spin-orbit coupling and a long injected spin lifetime.The first device is a spintronic LED which works with a magnetic electrode instead of an electron-hole electrode. The perovskite LED lights up with circularly polarized electroluminescence.

Researchers show how to create spin-valley half-metals

Researchers from Russia and Japan have shown, theoretically, that it is possible to create a new class of materials: spin-valley half-metals. These kind of devices could enable both spintronics valleytronics applications.

Spin-valley half-metal image (MIPT)

In "regular" half-metals, all the electrons that participate in electric currents have the same spin - and so the current is always spin-polarized. These materials have interesting applications for spintronics devices. In the new class of materials now proven theoretically to be possible, there are two valleys present - one providing electrons, one providing holes.

A lateral electric field can control the spin polarization in zigzag graphene ribbons

Researchers from Grennole Alpes University in France have demonstrated using atomistic calculations that a lateral electric field can be used to tune the carrier mobility and change the spin polarization of the current driving through zigzag graphene ribbons. The researchers say that these effects can be nicely exploited in spintronics devices.

Spin polarization in ZGNR image

The calculations predict a high variation of the carrier mobility, mean free path and spin polarization in the ZGNRs. It turns out that configurations with almost 100% spin-polarized current can be switched on and off.

JGU establishes a new spintronics junior research group

The Johannes Gutenberg University Mainz (JGU), with funding from the German Research Foundation (DFG), is setting up an Emmy Noether independent junior research group to study spintronics.

Skyrmions generated by hairy balls image

Specifically, the TWIST (Topological Whirls in SpinTronics) work group will study skyrmions - magnetic "particles" or nodes within a magnetic texture. Skyrmions are more stable than other magnetic structures and react particularly readily to spin currents - which makes them interesting for spintronics applications.