September 2022

Researchers from Germany's Forschungszentrum Juelich have reported an exotic electronic state, so-called Fermi Arcs, for the first time in a 2D material. Finding Fermi arcs in such a material may provide a link between novel quantum materials and their potential applications in a new generation of spintronics and quantum computing. 

The newly demonstrated Fermi arcs represent special—arc-like—deviations from the so-called Fermi surface. The Fermi surface is used in condensed matter physics to describe the momentum distribution of electrons in a metal. Normally, these Fermi surfaces represent closed surfaces. Exceptions such as the Fermi arcs are very rare and often are associated with exotic properties like superconductivity, negative magnetoresistance and anomalous quantum transport effects.

A University of Münster, University of Duisburg-Essen and University of Pittsburgh research team recently set out to advance the systematic development of spin-selective catalyst materials. To this end, the researchers related the catalytic activity of various inorganic spin-polarizing materials to direct measurements of spin selectivity. The focus is on oxide materials which were purposely grown with a chiral structure. In addition, the researchers also wanted to investigate the origin of spin polarization in these chiral materials. 

The team first examined chiral oxide catalysts—consisting in this case of thin, chiral copper oxide layers on a thin film of gold. The data measured showed that the spin polarization of the electrons depends on which of these layers the electrons come from. The team considers two effects to be responsible for this: the chirality-induced spin selectivity (CISS) effect and the magnetic arrangement in the chiral layers. The results are to help in the future production of spin-selective catalytic oxide materials, thus improving the efficiency of chemical reactions.

Researchers from Germany's Martin Luther University Halle-Wittenberg (MLU) have demonstrated that strong alternating magnetic fields can be used to generate a new type of spin wave. This is the first time this was accomplished as the phenomenon was previously only theoretically predicted. Thee team reported on their work and provided the first microscopic images of these spin waves.

The basic idea of spintronics is to use a special property of electrons (spin) for various electronic applications. The Spin is the intrinsic angular momentum of electrons that produces a magnetic moment. Coupling these magnetic moments creates the magnetism that could ultimately be used in information processing. When these coupled magnetic moments are locally excited by a magnetic field pulse, this dynamic can spread like waves throughout the material. These are referred to as spin waves or magnons.

Researchers from Columbia University, the University of Washington, New York University, and Oak Ridge National Laboratory have shown that magnons in CrSBr can pair up with another quasiparticle called an exciton, which emits light, offering the researchers a means to “see” the spinning quasiparticle.

As they perturbed the magnons with light, they observed oscillations from the excitons in the near-infrared range, which is nearly visible to the naked eye. “For the first time, we can see magnons with a simple optical effect,” said Xiaoyang Zhu from Columbia University .  

Scientists from India's B. P. Poddar Institute of Management & Technology, Maulana Abul Kalam Azad University of Technology and Meghnad Saha Institute of Technology, collaboration with the University of Western Australia, have used iron (Fe) quantum dot (QD) electrodes to determine the spin transport properties and quantum scattering transmission characteristics of DNA sensors at room temperature. 

Spintronics has shown great potential for the development of devices that require low power for operation, high density and high speed processing, all of which are ideal for electronic memory devices. These properties are used in optoelectronic devices, mainly for circularly polarized light. Interestingly, spintronics is also applied in a semiconductor tunnel junction.

Scientists have been looking for efficient methods to generate spin current. The photogalvanic effect, a phenomenon characterized by the generation of DC current from light illumination, is particularly useful in this regard. Studies have found that a photogalvanic spin current can be generated similarly using the magnetic fields in electromagnetic waves. However, there's a need for candidate materials and a general mathematical formulation for exploring this phenomenon.

Now, Associate Professor Hiroaki Ishizuka from Tokyo Institute of Technology (Tokyo Tech), along with his colleague Masahiro Sato, addressed these issues. In their recent study, they presented a general formula that can be used to calculate the photogalvanic spin current induced by transverse oscillating magnetic excitations. They then used this formula to understand how photogalvanic spin currents arise in bilayer chromium (Cr) trihalide compounds, namely chromium triiodide (CrI₃) and chromium tribromide (CrBr₃).