In a pioneering first, researchers at the Massachusetts Institute of Technology (MIT) have successfully measured the superfluid stiffness of magic-angle twisted bilayer graphene (MATBG), a key discovery that could unlock its potential for superconductivity and future applications in quantum computing. The breakthrough, outlined in a recent press release, represents a major step toward understanding the complex behavior of MATBG and its practical uses in emerging technologies.
Graphene, a material composed of a single layer of carbon atoms just one atom thick, has been a subject of intense research since its discovery. Known for its exceptional electrical conductivity, strength, and heat transfer properties, graphene has become a go-to material for a wide range of applications. In recent years, however, a novel structure—known as magic-angle twisted bilayer graphene—has captivated scientists due to its ability to exhibit superconductivity and other remarkable behaviors.
When two graphene sheets are stacked at a very precise “magic angle,” they form a twisted structure, which alters the interactions between the electrons. Unlike in most materials, where electrons repel each other, in MATBG, they instead form pairs that flow effortlessly through the material—creating a superfluid state. This behavior is crucial for the development of superconductors and quantum computing systems, where precise electron flow is essential.
The key to unlocking MATBG’s potential lies in understanding superfluid stiffness—the ease with which these electron pairs flow through the material. Joel Wang, a research scientist at MIT who contributed to the study, explained that superfluid stiffness is an important parameter that reveals how easily the electron pairs move, which directly impacts superconductivity. Measuring this stiffness can provide insights into the material’s behavior and help researchers optimize its properties for real-world applications.
Traditionally, measuring superfluid stiffness involves placing a superconducting material inside a microwave resonator, a device that oscillates at microwave frequencies. When the material is placed in the resonator, it alters the frequency, providing valuable data on the material’s superfluid stiffness. However, this technique was typically used for much larger, bulkier superconductors—far thicker and more substantial than the thin, delicate MATBG.
To adapt this method for MATBG, the team had to navigate the challenges of working with an ultrathin material, requiring careful attachment and lossless contact with the resonator. The researchers collaborated with MIT’s Will Oliver, an expert in delicate two-dimensional materials used in quantum computing. By connecting aluminum leads—common in quantum experiments—to the MATBG and linking them to the resonator, the team was able to send microwave signals through the system and measure the material’s kinetic inductance, which can then be used to calculate superfluid stiffness.
What they found was unexpected: the superfluid stiffness of MATBG was ten times larger than anticipated, with temperature dependencies that matched the predictions of quantum geometry theory. Miuko Tanaka, a former MIT postdoctoral fellow who worked on the project, noted the significance of this finding, highlighting the discrepancy between observed and predicted values as a “tenfold increase” that opens up new avenues for research.
The team attributes this enhanced stiffness to the quantum geometry inherent in the material’s structure, offering new insights into how MATBG behaves at quantum scales. These findings suggest that MATBG could be a key material in the development of future quantum computers, providing a more efficient and scalable way to manage quantum information.
This breakthrough marks an exciting chapter in materials science, offering new possibilities for superconductivity and quantum computing. As research continues to unfold, MATBG’s potential could play a crucial role in the evolution of quantum technologies, with MIT’s discovery setting the stage for further advancements in both fundamental physics and practical applications.
By Impact Lab
