Discover how a new method unlocks the secrets of magic-angle graphene’s superconductivity, paving the way for advances in quantum computing!
MIT and Harvard University researchers have directly measured superfluid stiffness in magic-angle graphene—a material composed of two or more atomically thin layers of graphene twisted at just the right angle to unlock exceptional properties, including unconventional superconductivity.
Magic-angle graphene holds great promise for future quantum computing technologies, but the exact mechanism behind its superconductivity remains a mystery. Measuring its superfluid stiffness provides valuable insight into this process. The team’s findings suggest that superconductivity in magic-angle graphene is primarily influenced by quantum geometry, which describes the abstract “shape” of quantum states within a material.
Magic Resonance
Scientists measure superfluid stiffness using microwave resonators with a characteristic resonance frequency. When a superconducting material is placed inside, it alters the device’s frequency and kinetic inductance, revealing properties related to superfluid stiffness. Traditional methods, however, work only with larger, thicker materials, making them unsuitable for atomically thin materials like MATBG.
Capturing the Signal
Measuring superfluid stiffness in MATBG required a seamless connection between the delicate material and the microwave resonator. Any loss in the connection could degrade or reflect the microwave signal, preventing accurate measurements.
The team has been refining techniques to attach fragile, two-dimensional materials for quantum computing applications precisely. Researchers applied these methods for this study to integrate a small MATBG sample with an aluminium microwave resonator.
They first assembled the MATBG structure and sandwiched it between insulating hexagonal boron nitride layers to preserve its properties. Then, they sharply etched the MATBG to expose a clean edge for direct contact with aluminium, the same material as the resonator, ensuring a strong superconducting connection.
Once connected, the team sent a microwave signal through the resonator and measured shifts in its resonance frequency. From this, they calculated MATBG’s kinetic inductance and its superfluid stiffness. The results were surprising—superfluid stiffness was ten times higher than predicted by conventional theories.
