Light isn’t just for seeing—it can also give things a push. When light travels, it carries energy and momentum, which is like motion energy.
Scientists have found a clever way to use this power to “spin” electrons and create currents in a material called graphene.
Their breakthrough, published on November 26, 2024, in Nature Photonics, could lead to new tools for controlling quantum materials and better understanding the strange behavior of electrons.
Electrons, the tiny particles inside atoms, are essential for many technologies.
Controlling how they move and interact with light is critical for advances like quantum computing and sensing. But getting electrons to respond to light in specific ways has been a big challenge—until now.
The scientists used a special kind of light that twists as it travels. This light, called orbital angular momentum light, spins like a corkscrew around its center. When you look at it straight on, it has a dark spot in the middle, like a vortex or tornado.
Using this twisted light, researchers managed to transfer its spinning motion to electrons in graphene. This is a big deal because it’s incredibly hard to make electrons react to such light. The trick was to “puff up” the electrons, giving them more space to move around and interact with the light’s twisty motion.
Graphene is an ultra-thin sheet of carbon atoms arranged like a honeycomb. It’s one of the best conductors of electricity, which means electrons can move through it easily.
By cooling graphene to just 4 degrees above absolute zero and applying a strong magnetic field, the researchers forced the electrons into loops called cyclotron orbits.
These loops were much bigger than the tiny paths electrons take around atoms, making it easier for the electrons to feel the effects of the twisted light.
The team hit the graphene with twisted light, giving the electrons a “spinning kick.” To make this work, they had to get the light and graphene perfectly aligned—a task that took months of trial and error.
When the light twisted clockwise, the electrons spun in one direction and created a current. When the light twisted counterclockwise, the current flipped direction.
Changing the magnetic field or adjusting the electrodes around the graphene sample confirmed that the current’s behavior matched the properties of the light’s twist.
Interestingly, when they tried using another kind of spinning light, called circularly polarized light, it barely made a current. This confirmed that the effect was specific to the unique twisting motion of orbital angular momentum light.
This method opens up exciting possibilities. For one, it provides a way to control electrons in quantum materials using light, which could lead to better quantum technologies. It might also enable new ways to measure the size and behavior of electrons in materials.
Electrons in quantum materials don’t act like ordinary particles. They follow strange rules and can exist in many states at once.
Using twisted light, scientists can “see” how far these electrons spread out and measure their quantum properties directly. This is a big step forward because it lets scientists not only observe but also manipulate electrons in precise ways.
The journey to this discovery wasn’t easy. Creating graphene samples with the right geometry took over a year.
The team worked with experts from the Polytechnic University of Milan in Italy to produce the samples they needed.
Once the samples were ready, aligning the twisted light with the graphene was another major hurdle. After weeks of fine-tuning, the team finally captured clear data showing the light’s effect on the electrons.
This discovery could lead to many new applications. Scientists might use twisted light to build better tools for studying quantum materials. For example, combining twisted light with interference measurements could act as a “microscope” for mapping the quantum behavior of electrons.
According to Mahmoud Jalali Mehrabad, one of the researchers, this technique is like finding the holy grail of electron control. “Not only can you detect electrons, but you can also manipulate them. That’s the ultimate goal.”
This breakthrough shows how powerful light can be—not just for illuminating our world, but for unraveling the mysteries of quantum physics.
Source: KSR.
