At a time when the quest is for smaller and faster units with infinite battery life, researchers from the University of California-Riverside have built topological insulators (TI) for quicker and longer-lasting electronics. In a paper published in “Science Advances” Jing Shi, a professor from the university wrote that his team has created a TI film just 25 atoms thick that adheres to an insulating magnetic film, creating a “heterostructure”, which makes TI surfaces magnetic at room temperatures and higher.
The surfaces of TI are only a few atoms thick and need little power to conduct electricity. If TI surfaces are made magnetic, current only flows along the edges of the devices, requiring even less energy. “Thanks to this so-called quantum anomalous Hall effect, or QAHE, a TI device could be tiny and its batteries long lasting,” Shi said. Topological insulators are the only materials right now that can achieve the coveted QAHE, but only after they are magnetized.
In 2015, Shi’s lab first created heterostructures of magnetic films and one-atom-thick graphene materials by using a technique called laser molecular beam epitaxy. The same atomically flat magnetic insulator films are critical for both graphene and topological insulators. “The materials have to be in intimate contact for TI to acquire magnetism. If the surface is rough, there won’t be good contact. We’re good at making this magnetic film atomically flat, so no extra atoms are sticking out,” Shi added.
The materials were then sent to its collaborators at Massachusetts Institute of Technology, who used molecular beam epitaxy to build 25 atomic TI layers on top of the magnetic sheets, creating the heterostructures, which were then sent back for device fabrication and measurements.