By stacking one-atom-thick sheets, like in a LEGO^® game, researchers can construct ultrathin materials with tailored electrical and optical properties. The game here offers much more room for creativity since the blocks can be assembled with more freedom than LEGO^® blocks. Sheets of graphene stacked slightly askew by a ‘magic angle’, for example, can superconduct (see March 2018 Meetings).

Another configuration not available in LEGO^® consists stretching one block before assembling, a possiblity that no one has yet investigated. This is precisely what Vincent Renard of Grenoble Alps University in France and colleagues have done. They found that graphene bilayers made of sheets with different amounts of tension display dramatically altered electrical properties. The new electrical properties suggest a physics similar to that observed at the magic angle.



On the left two rotated layers without strain. The super structure (called a moiré) results from the overlapping of the two atomic lattices. On the right, the top layer has been deformed by 10% in the horizontal direction. This deforms the moiré and has an important effect on the electronic properties of the system. In the experimental study a deformation of 0.36% only completely modified the electronic properties of the studied sample.

This article was selected as a Higlights by the Physics journal from the American Physics Society. We acknowledge the active participation of the Neel Laboratory in this project.