Researchers at the Massachusetts Institute of Technology (MIT) have previously found a particularly strange pattern in the “twisted” graphene structure, and now they’ve studied it more closely and found that the more layers it has, the better it will work.
Graphene is a 2D carbon nanomaterial consisting of a hexagonal hexagonal grid of a hexagonal structure of carbon atoms with a sp2 hybrid orbit. This makes them functionally two-dimensional, because the electrons that move through them can only move forward/backward and sideways, not above and below. This makes graphene very conductive.
When graphene layers are superimposed together, their electrical properties change. And in 2018, a team at the Massachusetts Institute of Technology found that when two layers of graphene were stacked slightly sloping together, something incredible happened. By twisting the top to a “magic angle” of 1.1 degrees, the double-layer structure can suddenly shift between the electrical insulator and the superconductor.
In two new studies, the same team has now studied these distorted double-layer graphene structures more closely. In the first study, the team tested the effects of different angles, using a scanning technique that was accurate enough to measure the difference in angle to 0.002 degrees. The team found that strange insulation and superconducting properties were more pronounced when the angle range was stuck at nearly 1.1 degrees. These effects appear to diminish in a stack with a large angle range.
“This is the first time that the entire structure has been mapped to see what the angle of distortion is in a particular area of the device,” said study author Pablo Jarillo-Herrero. “And we see that you can have a little bit of a change that can still show superconductivity and other strange physical phenomena, but not too much.” We’ve now determined how many distortion changes you can have and how many distortion changes will produce degradation effects. “
In the second study, the researchers conducted more experiments. When they stack four layers of graphene together and twist it to a magical angle, the structure becomes an insulator like a two-layer version. But this time, the team was able to use electric fields to fine-tune insulation, which had never been possible before.
The work is still in its early stages, but the team says the twisted graphene systems could eventually produce some unusual electronic devices.