Scientists at ETH Zurich have made a groundbreaking discovery, revealing a novel form of magnetism in moiré materials, which are artificially produced experimental substances. This unique magnetism, termed “kinetic magnetism,” was observed as electrons paired up into particles known as “doublons.”
The commonly known forms of magnetism include ferromagnetism and paramagnetism, where electron spins either align in the same direction or point in random directions, respectively. The ETH Zurich scientists delved into the magnetic properties of moiré materials crafted by stacking two-dimensional sheets of molybdenum diselenide and tungsten disulfide. These materials feature a lattice structure capable of housing electrons.
To investigate the magnetism of moiré materials, the researchers introduced electrons into the lattice by applying an electric current. Using a laser, they measured the reflection of light for different polarizations to determine the alignment of electron spins. Initially displaying paramagnetism, the material unexpectedly shifted to ferromagnetism as electrons filled the lattice beyond one electron per site, challenging the conventional exchange interaction mechanism.
Lead author Ataç Imamo?lu proposed a different mechanism: electrons forming pairs called “doublons” as they entered lattice sites, filling the lattice through quantum tunneling. As the electrons aligned their spins to minimize kinetic energy, ferromagnetism emerged. This “kinetic magnetism” had been theoretically predicted but had not been observed in solid materials until now.
While this discovery opens new avenues in understanding magnetism, the researchers aim to explore the phenomenon further, particularly its viability at higher temperatures. Notably, the experiment required the material to be cooled to just above absolute zero, and the practical applications of this kinetic magnetism could hold significant implications for future materials science and technology.
The research was published in the journal Nature.
Source: ETH Zurich