Researchers from the RIKEN Center for Emergent Matter Science (CEMS) and their collaborators have discovered a groundbreaking method to control superconductivity by twisting atomically thin layers within a layered device. By adjusting the twist angle, they were able to finely tune the “superconducting gap,” a key factor in the behavior of superconducting materials. This breakthrough, published in Nature Physics, could pave the way for more energy-efficient technologies and advancements in quantum computing.
The superconducting gap is the energy threshold required to break apart Cooper pairs—bound electron pairs that enable superconductivity at low temperatures. A larger gap allows superconductivity to persist at higher, more accessible temperatures, which is crucial for practical applications. Tuning this gap is also essential for optimizing the behavior of Cooper pairs at the nanoscale, enhancing the functionality of quantum devices.
Previous efforts to control the superconducting gap have primarily focused on “real space,” which involves the physical positioning of particles. However, achieving control in “momentum space”—a different mapping that shows the energy state of the system—has been challenging. Fine-tuning the gap in momentum space is critical for the development of next-generation superconductors and quantum devices.
To achieve this, the research team worked with ultrathin layers of niobium diselenide, a well-known superconductor, deposited on a graphene substrate. Using advanced imaging and fabrication techniques, such as spectroscopic-imaging scanning tunnelling microscopy and molecular beam epitaxy, they precisely adjusted the twist angle of the layers. This adjustment resulted in measurable changes in the superconducting gap within momentum space, providing a new method for precisely tuning superconducting properties.
Masahiro Naritsuka of CEMS, the first author of the paper, explained, “Our findings demonstrate that twisting provides a precise control mechanism for superconductivity by selectively suppressing the superconducting gap in targeted momentum regions. One surprising discovery was the emergence of flower-like modulation patterns within the superconducting gap that do not align with the crystallographic axes of either material. This underscores the unique role of twisting in shaping superconducting properties.”
Tetsuo Hanaguri of CEMS, the last author, added, “In the short term, our research deepens the understanding of superconducting systems and inter-layer interactions, advancing the design of superconductors with tailored properties. In the long term, it lays the foundation for developing energy-efficient technologies, quantum computing, and beyond. Next steps involve investigating whether magnetic layers can be integrated into the structure to enable both spin and momentum selectivity. These advances could unlock new research opportunities and pave the way for developing innovative materials and devices.”
This research marks a significant step forward in the control of superconductivity, offering a new method to fine-tune superconducting properties through the manipulation of atomically thin layers. The findings not only enhance our understanding of superconducting systems but also open up new possibilities for the development of energy-efficient technologies and quantum computing. Future research will explore the integration of magnetic layers, potentially leading to even more advanced materials and devices.
Add comment