Opto-spintronics

Researchers from the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Sorbonne Université CNRS, INRS-EMT, FERMI, Uppsala University, University of York and University of Hull have developed a non-thermal method to alter magnetization using XUV radiation, utilizing the inverse Faraday effect in an iron-gadolinium alloy. This approach enables significant magnetization changes without the usual thermal effects, promising enhancements in ultrafast magnetism technologies. 

Intense laser pulses can be used to manipulate or even switch the magnetization orientation of a material on extremely short time scales. Typically, such effects are thermally induced, as the absorbed laser energy heats up the material very rapidly, causing an ultrafast perturbation of the magnetic order. The research team has now demonstrated an effective non-thermal approach of generating large magnetization changes. By exposing a ferrimagnetic iron-gadolinium alloy to circularly polarized pulses of extreme ultraviolet (XUV) radiation, they could reveal a particularly strong magnetic response depending on the handedness of the incoming XUV light burst (left- or right-circular polarization).

Researchers from National Renewable Energy Laboratory (NREL), University of Utah, Université de Lorraine CNRS and University of Colorado Boulder have improved upon their previous work, that included incorporating a perovskite layer that allowed the creation of a new type of polarized light-emitting diode (LED) that emits spin-controlled photons at room temperature without the use of magnetic fields or ferromagnetic contacts. In their latest work, they have gone a step further by integrating a III-V semiconductor optoelectronic structure with a chiral halide perovskite semiconductor.

The team transformed an existing commercialized LED into one that also controls the spin of electrons. The results could provide a pathway toward transforming modern optoelectronics, a field that relies on the control of light and encompasses LEDs, solar cells, and telecommunications lasers, among other devices.

Researchers at the University of Cambridge,  University of Manchester, University of Oxford,  Swansea University, Jilin University, University of Namur, University of Mons, Donostia International Physics Centre, University of Würzburg have developed a way to control the interaction of light and quantum 'spin' in organic semiconductors, that even works at room temperature.

The international team of researchers has found a way to use particles of light as a 'switch' that can connect and control the spin of electrons, making them behave like tiny magnets that could be used for quantum applications. The researchers designed modular molecular units connected by tiny 'bridges'. Shining a light on these bridges allowed electrons on opposite ends of the structure to connect to each other by aligning their spin states. Even after the bridge was removed, the electrons stayed connected through their aligned spins.

Researchers from the Technion – Israel Institute of Technology, Tel Aviv University and China's Shanghai Jiao Tong University have developed a coherent and controllable spin-optical laser based on a single atomic layer. This was enabled by coherent spin-dependent interactions between a single atomic layer and a laterally confined photonic spin lattice, the latter of which supports high-Q spin-valley states through the photonic Rashba-type spin splitting of a bound state in the continuum.

The team's achievement could pave the way towards studying coherent spin-dependent phenomena in both classical and quantum regimes, opening new horizons in fundamental research and optoelectronic devices exploiting both electron and photon spins.

Researchers from the Hebrew University of Jerusalem in Israel have made a recent discovery that could change the face of spintronics research.

A spintronics device developed by Professor Capua's lab

They discovered that the most important equation used to describe magnetization dynamics, namely the Landau-Lifshitz-Gilbert (LLG) equation, also applies to the optical domain. Consequently, they found that the helicity-dependent optical control of the magnetization state emerges naturally from their calculations. This is a very surprising result since the LLG equation was considered to describe much slower dynamics and it was not expected to yield a meaningful outcome also at the optical limit.

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.

An international collaboration involving the Irradiated Solids Laboratory at EPFL has published a paper detailing the mechanisms for detecting circularly polarized light using spin-optoelectronic devices called spin photodiodes.

"In this work, we combined spintronics with optics. This is spin-optoelectronics," explains Henri-Jean Drouhin, co-author of the study published and head of the 'Physics and Chemistry of Nano-objects' group at the Irradiated Solids Laboratory (LSI). Light particles, photons, also have a spin. This spin manifests itself in the fact that light can be right- or left-handed circularly polarized (which means that the electric field of the light winds to the right or left like a helix in the direction of propagation of the photons). When this light hits the device designed by the researchers, photons can excite electrons in the material. The spin of these electrons then adopts a preferential direction that depends on the photon spin. Knowing how to selectively extract the electrons therefore makes it possible to obtain information on the polarization of the incident light, making these devices 'spin photodiodes', in contrast to conventional photodiodes that measure the intensity of the light.

A team of researchers from Sweden, Finland and Japan have designed a semiconductor component in which information can be efficiently exchanged between electron spin and light at room temperature and above.

Developments in spintronics in recent decades have been based on the use of metals, and these have been highly significant for the possibility of storing large amounts of data. There would, however, be several advantages in using spintronics based on semiconductors, in the same way that semiconductors form the backbone of today's electronics and photonics.

A team of researchers from the National Renewable Energy Laboratory (NREL) and the University of Utah has developed a new type of LEDs that utilizes spintronics without needing a magnetic field, magnetic materials or cryogenic temperatures.

“The companies that make LEDs or TV and computer displays don’t want to deal with magnetic fields and magnetic materials. It’s heavy and expensive to do it,” said Valy Vardeny, distinguished professor of physics and astronomy at the University of Utah. “Here, chiral molecules are self-assembled into standing arrays, like soldiers, that actively spin polarize the injected electrons, which subsequently lead to circularly polarized light emission. With no magnetic field, expensive ferromagnets and with no need for extremely low temperatures. Those are no-nos for the industry.”

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.