2023-12-07 10:15:56
Graphene, carbon so thin that its thickness is a single atom, is a material full of surprises. Scientists have now managed to convert micrometric graphene disks into very powerful temporary magnets.
Graphene, discovered in 2004, has extraordinary properties. Among them is its ability to conduct electricity extremely well, and that is precisely what researchers from Germany, Poland, India and the United States have taken advantage of.
The team, including Stephan Winnerl from the Helmholtz Center Dresden-Rossendorf (HZDR) in Germany and Jeong Woo Han from the University of Duisburg-Essen in Germany, applied thousands of tiny micrometer-sized graphene disks on a small chip using established semiconductor techniques. This chip was then exposed to a particular type of radiation located between the microwave and infrared ranges: short pulses with a wavelength on the order of terahertz.
To achieve the best possible conditions, the team used a special light source for the experiment: the FELBE free electron laser at the HZDR, which can generate extremely intense terahertz pulses. The result was astonishing: The tiny graphene disks briefly became something that could be described as electromagnets.
Winnerl and his colleagues managed to generate magnetic fields of the order of 0.5 Tesla, which is equivalent to approximately ten thousand times the Earth’s magnetic field. These were short magnetic pulses, only about ten picoseconds (trillionths of a second).
When a pulse of circularly polarized light (shown in red) hits a micrometer-sized graphene disk (shown in gray), a magnetic field (black lines) is created for a very brief instant. (Image: Uta Lucchesi / HZDR)
The prerequisite for success: the researchers had to polarize the terahertz flashes in a specific way. Specialized optics changed the direction of oscillation of the radiation so that it moved, figuratively, helically through space.
When these circularly polarized flashes collided with the micrometer-sized graphene disks, the decisive effect occurred: stimulated by the radiation, the free electrons in the disks began to circulate, like water in a bucket stirred with a ladle. The laws of physics state that a circulating current always generates a magnetic field. And that’s why the graphene discs transformed for an instant into tiny electromagnets.
Winnerl and his colleagues present the technical details of their advance in the academic journal Nature Communications, under the title “Strong transient magnetic fields induced by THz-driven plasmons in graphene disks.” (Source: NCYT from Amazings)
#carbon #magnetic #laser