Twisted Graphene Reveals Double-Dome Superconductivity Controlled by Electric Field

janrinok writes:

https://phys.org/news/2025-10-graphene-reveals-dome-superconductivity-electric.html

Superconductivity is a phenomenon where certain materials can conduct electricity with zero resistance. Obviously, this has enormous technological advantages, which makes superconductivity one of the most intensely researched fields in the world.

But superconductivity is not straightforward. Take, for example, the double-dome effect. When scientists plot where superconductivity appears in material as they change how many electrons are in it, the material's superconducting regions sometimes look like two separate "domes" on a graph.

In other words, the material becomes superconducting, then stops, then becomes superconducting again as we keep changing its electron density.

Double-dome superconductivity has been seen before in some complex materials, such as graphene. Graphene is essentially a sheet of carbon atoms just one atom thick linked together in a honeycomb pattern. Still, it has transformed the field of quantum materials research because it features some really strange effects.

For example, when we stack two graphene layers and twist them at specific angles, the electrons in the graphene behave in new and unexpected ways, creating quantum phases like magnetism, electrical insulation, and, of course, superconductivity.

But there is an even more complex structure of graphene that takes this further by adding a third layer, making the system even more complex and tunable: Magic-angle twisted trilayer graphene (MATTG). With MATTG, researchers can now observe and control a double-dome pattern of superconductivity that was previously only suspected in graphene systems.

In a new study published in Nature Physics, a team led by Mitali Banerjee at EPFL, together with partners in Switzerland, the U.K., and Japan, has shown that MATTG allows direct control of the double-dome superconductivity pattern. By carefully stacking the layers and adjusting the electric field, the researchers could fine-tune the system and track where superconductivity appeared or disappeared as they varied the number of electrons.

Their experiments, supported by theory, revealed that two distinct superconducting regions-the domes-show up as they gradually changed the electron count in MATTG. The work sheds light on how unconventional superconductivity can be created and controlled in 2D materials.

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