Research / Technical - Page 8

Researchers from King Abdullah University of Science and Technology (KAUST) have shown that spintronics-based protective “logic locks” could be incorporated into the integrated circuits of electronic chips to defend chip security. This means that next-gen electronics could feature enhanced security systems built directly into their circuitry to help fend off malicious attacks. 

“The need for hardware-based security features reflects the globalized nature of modern electronics manufacture,” explains Yehia Massoud from KAUST. Electronics companies usually employ large specialized, external foundries to produce their chips, which minimizes costs but introduces potential vulnerabilities to the supply chain. The circuit design could simply be illegally copied by an untrusted foundry for counterfeit chip production or could be maliciously modified by the incorporation of “hardware Trojans” into the circuitry that detrimentally affects its behavior in some way.

Researchers at Beijing Institute of Technology and California Institute of Technology have developed a new theory and numerical calculations to predict spin decoherence in materials with high accuracy. This addresses the issue of spin coherence: quantum states can be easily disrupted, which is a problem when attempting to use them in a device; the electron spins need to preserve their quantum state for as long as possible to avoid loss of information. Spin coherence is so delicate that even the tiny vibrations of the atoms that make up the device can alter the spin state irreversibly.

Marco Bernardi, professor of applied physics, physics and materials science, explains: "Existing theories of spin relaxation and decoherence focus on simple models and qualitative understanding. After years of systematic efforts, my group has developed computational tools to study quantitatively how electrons interact and move in materials. This new paper has taken our work a few steps further: we have adapted a theory of electrical transport to study spin, and discovered that this method can capture two main mechanisms governing spin decoherence in materials—spin scattering off atomic vibrations, and spin precession modified by atomic vibrations. This unified treatment allows us to study the behavior of the electron spin in a wide range of materials and devices essential for future quantum technologies".

Researchers from Germany's Max Planck Institute of Microstructure Physics have reported a lift-off and transfer method to fabricate three-dimensional racetrack memories from freestanding magnetic heterostructures grown on a water-soluble sacrificial release layer.

The fabrication of three-dimensional nanostructures is key to the development of next-generation nanoelectronic devices with a low device footprint. Magnetic racetrack memories encode data in a series of magnetic domain walls that are moved by current pulses along magnetic nanowires. To date, most studies have focused on two-dimensional racetracks.

A new instrument called ALICE II is available at BESSY II, that allows magnetic X-ray scattering in reciprocal space using a new large area detector. Recntly, researchers from HZB and Technical University Munich demonstrated the performance of ALICE II by analyzing helical and conical magnetic states of an archetypal single crystal skyrmion host.

The new instrument was conceived and constructed by HZB physicist Dr. Florin Radu and the technical design department at HZB in close cooperation with Prof. Christian Back from the Technical University Munich and his technical support. It is now available for guest users at BESSY II as well.

Scientists from the University of Warsaw, Poland-based Military University of Technology, CNR Nanotec, the University of Southampton and the University of Iceland have designed a new photonic system with electrically tuned topological features, constructed of perovskites and liquid crystals. The new system can be used to create efficient light sources.

Perovskites are highly-studied materials that have the potential to revolutionize the solar energy fields, among others. These are durable and easy-to-produce materials, the special property of which is a high solar light absorption coefficient and they are therefore used to develop new, more efficient photovoltaic cells. In recent years, the emission properties of these materials, so far underestimated, have been used.

A correlated phase that  electrons can take on is magnetic order, in which they align their spin in the same direction. Traditionally, the ability to manipulate magnetic order within a 2D semiconductor has been limited; scientists have used external magnetic fields, which limit technological integration and potentially conceal interesting phenomena. Now, researchers from the University of Chicago’s Pritzker School of Molecular Engineering (PME) have discovered how to use nanoscale, low-power laser beams to precisely control magnetism within a 2D semiconductor. Their approach could have implications for both studying the emergence of the correlated phase as well as designing new optoelectronic and spintronic devices.

“The fact that we can now use light to manipulate electrons in this way means we have unprecedented control over this magnetic order,” said Asst. Prof. Alex High, the senior author of the new work.

Researchers from Oak Ridge National Laboratory, Helmholtz-Zentrum Berlin (HZB) and University of Amsterdam have used inelastic neutron scattering and methods of integrability to experimentally observe and theoretically describe a local, coherent, long-lived, quasiperiodically oscillating magnetic state emerging out of the distillation of propagating excitations following a local quantum quench in a Heisenberg antiferromagnetic chain.

This “quantum wake” displays similarities to Floquet states, discrete time crystals and nonlinear Luttinger liquids. The team also showed how this technique reveals the non-commutativity of spin operators, and is thus a model-agnostic measure of a magnetic system’s “quantumness.”

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.