All magnets—from simple souvenirs hanging from refrigerators to disks that provide memory for computers, to powerful versions used in research labs—contain rotating quasiparticles called magnons. The direction in which a magnon spins can affect the orientation of its neighbors, which affects the spins of its neighbors, and so on, creating so-called spin waves. Information can be transported more efficiently than electricity via spin waves, and magnons can act as “quantum interconnects” that “glue” qubits into powerful computers.
Magnons have enormous potential, but they are often difficult to spot without bulky lab equipment. Such a setup is suitable for conducting experiments, but not for developing devices, such as magnetic devices and so-called spintronics, said Xiaoyang Zhu, a researcher at Columbia University. However, magnon observations can be made simpler with the right material: a magnetic semiconductor called chromium bromide (CrSBr), which can be exfoliated into atomically thin two-dimensional layers, synthesized in the lab of chemistry professor Xavier Roy .
in a new article natureZhu and collaborators at Columbia University, Washington University, New York University and Oak Ridge National Laboratory showed that magnons in CrSBr can pair with another type of quasiparticle called excitons, which emit light, giving researchers a way to “See” the spinning quasiparticle.
When they perturbed the magnons with light, they observed the excitons oscillate in the near-infrared range, which is almost visible to the naked eye. “For the first time, we can see magnons with simple optical effects,” Zhu said.
The results could be viewed as quantum transduction, or the conversion of one “quantum” of energy into another, said first author Yin Jun (Younis) Pei, a postdoctoral fellow in Zhu’s lab. Excitons are four orders of magnitude more energetic than magnons; now, because they are so closely paired together, we can easily observe tiny changes in magnons, Bae explained.This conversion could one day enable researchers to build quantum information networks that can take information from spin-based qubits — which typically need to be separated by a few millimeters from each other — and convert it into light, a kind of Forms of energy that can transmit information up hundreds of miles through fiber optics
The coherence time — how long the oscillations can last — was also significant, Zhu said, lasting much longer than the experiment’s 5-nanosecond limit. Even if CrSBr devices are made from only two atomically thin layers, this phenomenon can propagate beyond 7 microns and persist, raising the possibility of building nanoscale spintronic devices. These devices could one day be a more efficient replacement for today’s electronics. Unlike electrons in an electric current, which encounter resistance as they travel, no particles actually move in a spin wave.
From here, the researchers plan to explore the quantum information potential of CrSBr, as well as other candidate materials. “In MRSEC and EFRC, we are exploring the quantum properties of several 2D materials that you can stack like paper to create all kinds of new physical phenomena,” Zhu said.
For example, if magneto-exciton coupling could be found in other kinds of magnetic semiconductors with slightly different properties than CrSBr, they might emit light in a wider range of colors.
“We are assembling toolboxes to build new devices with customizable properties,” Zhu added.
Unique quantum material could enable ultra-powerful compact computers
Youn Jue Bae et al., Exciton-coupled coherent magnons in 2D semiconductors, nature (2022). DOI: 10.1038/s41586-022-05024-1
Provided by Columbia University
Citation: Scientists in 2D magnets retrieved on 8 September 2022 from https://phys.org/news/2022-09-scientists-2d-magnet.html (7 September 2022) spin
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