Scientists ‘see’ spinning quasiparticles in a 2D magnet

Pairing between magnons and excitons will allow researchers to see spin directions, an important consideration for many quantum applications. 1 credit

New research reveals that spinning quasiparticles, or magnons, light up when paired with a light-emitting quasiparticle, or exciton, with potential quantum information applications.

All magnets contain spinning quasiparticles called magnons. This is true of all magnets, from simple keepsakes hanging on your fridge, to disks that store your computer’s memory, to powerful versions used in research labs. The direction of rotation of a magnon can influence that of its neighbor, which in turn affects the rotation of its neighbor, and so on, producing what are called spin waves. Spin waves can potentially transmit information more efficiently than electricity, and magnons can serve as “quantum interconnects” that “glue” quantum bits together in powerful computers.

Although magnons have enormous potential, they are often difficult to detect without bulky laboratory equipment. According to Columbia researcher Xiaoyang Zhu, such setups are perfect for conducting experiments, but not for developing devices, such as magnonic devices and so-called spintronics. However, seeing magnons can be made much simpler with the right material: a magnetic semiconductor called chromium sulfide bromide (CrSBr) that can be peeled into atom-2D thin layers, synthesized in the laboratory of Professor Xavier Roy of the Chemistry Department.

“For the first time, we can see magnons with a simple optical effect.”
Xiaoyang Zhu

In a new article published in the journal Nature on September 7, Zhu and his collaborators at Columbia, the University of Washington, New York Universityand Oak Ridge National Laboratory show that CrSBr magnons can associate with another quasiparticle called an exciton, which emits light, giving researchers a mechanism to “see” the spinning quasiparticle.

By perturbing the magnons with light, they observed oscillations of the excitons in the near-infrared region, which is almost visible to the naked eye. “For the first time, we can see magnons with a simple optical effect,” Zhu said.

The results can be thought of as quantum transduction, or the conversion of one “quanta” of energy into another, said first author Youn Jun (Eunice) Bae, a postdoc in Zhu’s lab. The energy of excitons is four orders of magnitude greater than that of magnons; now, because they pair so tightly, we can easily observe tiny changes in the magnons, Bae explained. This transduction could one day allow researchers to build quantum information networks that can take information from spin-based quantum bits – which typically need to be located within millimeters of each other – and convert it into light. , a form of energy capable of transferring information upwards. hundreds of kilometers away via fiber optics.

Zhu said the coherence time – how long the oscillations can last – was also remarkable, lasting much longer than the experiment’s five nanosecond limit. The phenomenon could travel more than seven micrometers and persist even when the CrSBr devices were made of only two thin layers of atoms, which opens the possibility of building spintronic devices at the nanometer scale. These devices could one day be more efficient alternatives to today’s electronics. Unlike electrons in an electric current which encounter resistance as they move, no particle actually moves in a spin wave.

From there, the scientists plan to explore the quantum information potential of CrSBr, as well as other candidate materials. “In MRSEC and EFRC, we explore the quantum properties of multiple 2D materials that you can stack like papers to create all kinds of new physical phenomena,” Zhu said.

For example, if the magnon-exciton coupling can be found in other types of magnetic semiconductors with slightly different properties from CrSBr, they could emit light in a wider color range. “We are assembling the toolkit to build new devices with customizable properties,” Zhu said.

Reference: “Coherent Excitation-Coupled Magnons in a 2D Semiconductor” by Youn Jue Bae, Jue Wang, Allen Scheie, Junwen Xu, Daniel G. Chica, Geoffrey M. Diederich, John Cenker, Michael E. Ziebel, Yusong Bai, Haowen Ren, Cory R. Dean, Milan Delor, Xiaodong Xu, Xavier Roy, Andrew D. Kent, and Xiaoyang Zhu, September 7, 2022, Nature.
DOI: 10.1038/s41586-022-05024-1

The work was supported by Columbia’s NSF-funded Materials Science and Engineering Research Center (MRSEC), with material created in the DOE-funded Energy Frontiers Research Center (EFRC). .

About Juana Jackson

Check Also

AC Milan vs Napoli – Football Match Report – 18 September 2022

A brilliant header from Napoli striker Giovanni Simeone helped his side seal a 2-1 victory …