Graphene, a material consisting of a sheet of carbon atoms arranged in a honeycomb pattern, has proved promising for various technological applications. Materials in which several layers of graphene are stacked together can exhibit different advantageous properties.
Researchers at Cornell University in the U.S., the National Institute for Materials Science in Japan and the Max Planck Institute for the Structure and Dynamics of Matter in Germany investigated the properties of rhombohedral hexalayer graphene, which includes six graphene layers shifted sideways in a repeating pattern.
Their paper, published in Nature Physics, reports various quantum states in this material under different conditions.
"Our discovery was somewhat unexpected," Xiaomeng Liu, senior author of the paper, told Phys.org. "We originally set out to study twisted rhombohedral graphene, hoping to create isolated topological bands. However, in one device made by stacking two three-layer graphene sheets, the layers relaxed into alignment, forming rhombohedral six-layer graphene."
The researchers' initial measurements performed on rhombohedral six-layer graphene hinted at behavior that was not reported in earlier studies focusing on five-layer graphene. This inspired them to explore the material's phase diagram, a graph describing the states that a material undergoes in different conditions.
"We were particularly intrigued by a strongly correlated semimetallic regime, where electrons and holes coexist and interact," said Liu.
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