Superconductivity and the Magic Angle of Graphene
Superconductivity is a fascinating physical phenomenon that allows the flow of electric current without any resistance, offering vast potential for improving energy efficiency and quantum computing technologies. Until now, this phenomenon has only been achievable at extremely low temperatures. Thanks to recent research at the Massachusetts Institute of Technology (MIT), new discoveries in twisted trilayer graphene with a magic angle suggest the possibility of achieving superconductivity under more practical and favorable conditions.
Graphene and Its Magic Angle
Graphene is a single layer of carbon atoms arranged in a hexagonal lattice resembling a wire mesh. In the last decade, scientists discovered that stacking two layers of graphene at a specific angle can lead to new and exciting electronic properties. In 2018, a team of researchers led by Professor Pablo Jarillo-Herrero successfully produced magic-angle graphene for the first time, sparking a new research field known as “twistronics.”
Twistronics studies the unexpected effects that arise when ultra-thin materials are stacked and rotated at precise angles. This field has helped uncover new phenomena in graphene, including unconventional superconductivity.
Understanding the Superconducting Gap
The MIT team measured the superconducting gap in twisted trilayer graphene, which indicates the strength of the superconducting state at various temperatures. They found that this gap is entirely different from what is observed in traditional superconductors, suggesting that the mechanism by which the material becomes superconducting relies on an unconventional process.
Sean Sun, a co-author of the study, states that the superconducting gap provides a clue about the type of mechanism that could lead to room-temperature superconductors, which would be beneficial for society.
The Role of Electrons in Superconductivity
Superconductivity occurs when electrons form pairs instead of scattering away as they move through a material. In traditional superconductors, electrons in these pairs are far apart and weakly bound. However, in magic-angle graphene, there are signs that these pairs are strongly bound, indicating something entirely different in this material.
Researcher Park believes that magic-angle graphene operates differently from traditional superconductors, where strong electronic interactions, rather than atomic lattice vibrations, help electrons form pairs.
New Techniques for Exploring the Quantum World
To confirm that magic-angle graphene indeed exhibits unconventional superconductivity, researchers used a technique known as tunneling spectroscopy. At this level, electrons behave as both particles and waves, allowing them to “tunnel” through barriers that would typically stop them. By studying how easily electrons pass through the material, researchers can determine how strongly they are bound within it.
Park’s team developed a new platform combining tunneling spectroscopy with electrical transport measurements, allowing them to observe the formation of the superconducting gap directly. This method can reveal how electron pairs form and compete with other states, paving the way for designing and controlling new superconductors and quantum materials.
Conclusion
Recent discoveries in magic-angle graphene suggest the possibility of an unconventional mechanism for superconductivity, opening new avenues for developing room-temperature superconductors. This research contributes to a deeper understanding of quantum materials and offers new potential for advanced technological applications. With support from various research institutions, the MIT team continues to explore twisted and layered materials to identify new candidates for future technology.