(Yaroslav Kushta/Getty Images)
Scientists have recently discovered an interaction between an electromagnetic wave and its own magnetic component as it passes through a material, updating a 180-year-old assumption that only accounted for the interaction between light and its electric field.
This phenomenon, the Faraday effect (FE), was first described in 1845 by Michael Faraday, providing some of the earliest evidence of interaction between magnetism and light waves.
It describes how a beam of light passing through a transparent material is affected when that material is subjected to a magnetic field. Specifically, this changes the direction of polarization of that light beam.
For a simplified perspective, light can be unpolarized or polarized. When light is unpolarized, its electromagnetic oscillations occur in various directions (perpendicular to its plane of travel).
Yet when light is polarized, these oscillations are ordered along a single direction – imagine pulling out a ruffled, fuzzy sweater from the closet and smoothing down its fibers.
Illustration depicting the Faraday effect.
(Wikimedia Commons/DrBob/CC-BY-SA 3.0)
Last year, the research team from the Hebrew University of Jerusalem demonstrated experimentally a subtle but clear influence of the magnetic side in the opposite of FE, where light's polarization creates a magnetic moment in a material.
In their new study, the researchers combined their experiment's findings with complex calculations based on the Landau–Lifshitz–Gilbert equation, which describes the dynamics of magnetism in solid materials, to determine whether this same subtle interplay may also be at work in the Faraday effect itself.
They used physical models of Terbium-Gallium-Garnet, a crystal that can be magnetized and is commonly used in fiber optics and telecom technologies, to base their calculations on.
The calculations suggest that light's magnetic field contributes about 17 percent of the FE in visible wavelengths and 70 percent in infrared wavelengths – far from insignificant, as previously assumed.
As a result, they show that the FE is directly influenced by the oscillating magnetic field of light, and not just its electric field, as was believed.
"Light doesn't just illuminate matter, it magnetically influences it. The static magnetic field 'twists' the light, and the light, in turn, reveals the magnetic properties of the material," physicist Amir Capua explains.
"What we've found is that the magnetic part of light has a first-order effect, it's surprisingly active in this process."
Therefore, this research has found another way for light's magnetic field to interact with matter – not by interacting with an electron's charge, but by interacting with another of its essential aspects, its spin, because every electron in every piece of matter has both charge and spin.
Capua described the breakthrough for ScienceAlert:
"At the heart of this effect is a basic principle that we've identified. You can, in very general terms, imagine the electron's spin as a tiny charge that spins about its axis, almost like a miniature top. In order to interact with the 'spinning electron' and divert the direction of its spin axis, the magnetic field that interacts with it also needs to "spin," namely, it needs to be circularly polarized."
Capua adds that this "creates a nicely balanced picture: the electrical field exerts a linear force on the charge while a 'spinning' circularly polarized magnetic field exerts a torque on the spin of the electron."
Discovering this overlooked interaction in the established FE could give scientists a way to more precisely control light and matter, potentially leading to advancements in sensing, memory, and computing, such as quantum computer innovations through higher-precision control of spin-based quantum bits.
Additionally, the field of spintronics uses electron spins, instead of charges, to store and manipulate information.
"What this discovery suggests is that you could control magnetic information directly with light," says electrical engineer Benjamin Assouline.
Finally, this work is tantalizing because it reminds us of one of the cornerstones of science – namely, that researchers may discover other as-yet unknown properties of light or other electromagnetic phenomena at any time, even in well-established models.
The Life of Earth
https://chuckincardinal.blogspot.com/
No comments:
Post a Comment
Stick to the subject, NO religion, or Party politics