Graphene, a two-dimensional material consisting of a single layer of carbon atoms arranged in a hexagonal lattice, has garnered significant attention in the scientific community due to its unique properties and potential applications in a wide range of fields. Graphene has many important applications for instance, graphene is an excellent conductor of electricity, which makes it a promising material for use in electronics. It has extremely high electron mobility, which means that electrons can move through it very quickly. This property makes graphene ideal for use in high-speed transistors and other electronic devices. Because of Graphene’s large surface area and high conductivity make it an ideal material for energy storage applications. It has been used in the development of supercapacitors, which can store and release energy quickly and efficiently. Furthermore, Graphene is highly sensitive to changes in its environment, which makes it an ideal material for use in sensors. It has been used to develop sensors for detecting gases, chemicals, and even single molecules. Other exciting applications are in the field of biomedicine. Its high surface area and unique properties make it useful for drug delivery, bioimaging, and tissue engineering and because of Graphene’s strength and durability make it a promising material for use in structural applications. It has been used in the development of lightweight and strong composites, as well as in the construction of buildings and other structures.
The story of Graphene discovery goes back to the year 2004, when researchers discovered graphene, a form of carbon that has garnered immense interest from both scientists and engineers due to its unique properties. Graphene consists of a single layer of carbon atoms arranged in a honeycomb-like lattice pattern, and when multiple layers of graphene are stacked on top of each other, the resulting material can exhibit vastly different electronic properties depending on the alignment of those layers in relation to one another. When two layers of graphene are twisted by just 1.05 degrees in relation to one another, the resulting stack can either conduct electricity with no resistance, making it a superconductor, or completely block the passage of electricity, making it an insulator. This finding has been dubbed the “magic angle” and has opened up new avenues for exploring the properties of graphene-based materials.
Recently, researchers at the California Institute of Technology (Caltech) led by Stevan Nadj-Perge, assistant professor of applied physics and materials science have discovered that tungsten diselenide, a wonder material with special optical and electrical properties, can enhance the electrical properties of graphene in ways that enrich our understanding of superconductivity and pave the way for engineering more robust and highly tunable graphene-based superconductors. Tungsten diselenide is not just a rival to graphene, but it is also a complement to it. By adding tungsten diselenide to graphene, the researchers at Caltech have managed to significantly improve upon the fragile superconductivity of untwisted bilayers of graphene. The research work is now published in the peer-reviewed journal Nature.
The research team discovered that when tungsten diselenide is placed on top of graphene bilayers, the untwisted graphene’s superconductivity is greatly improved. Notably, the superconducting critical temperature is enhanced by a factor of 10. By being in close proximity to graphene, tungsten diselenide bestows the benefits of the “magic angle” twist to the more mass-producible untwisted graphene. This finding provides new insight into the nature of superconductivity and suggests strategies for enhancing superconductivity in other related graphene-based materials.
The high level of tunability in these graphene bilayer devices opens up possibilities for future applications. For example, by applying electric fields, researchers can add or remove electrons from the bilayer as well as push them toward and away from tungsten diselenide. This allows for careful study of the enhancement of superconductivity in the system. One of the main advantages of untwisted graphene superconductors compared to their twisted counterparts is that they are much cleaner in terms of disorder and defects, and technically much easier to fabricate. That implies these structures may be more suited for applications where one would need to make many identical copies of the same device architecture.
Graphene’s unique properties and potential applications make it an important material in science and engineering. Ongoing research is focused on developing new applications and technologies that harness the full potential of this remarkable material. The discovery that tungsten diselenide can enhance the electrical properties of graphene provides new insight into the nature of superconductivity and suggests strategies for enhancing superconductivity in other related graphene-based materials. The high level of tunability in graphene bilayer devices opens up possibilities for future applications, and untwisted graphene superconductors may be more suited for applications where identical copies of the same device architecture need to be produced. The research by Professor Stevan Nadj-Perge and co-workers paves the way for the development of new and improved graphene-based materials with a wide range of applications in fields such as electronics, energy, and biotechnology.
Zhang, Y., Polski, R., Thomson, A. et al. Enhanced superconductivity in spin–orbit proximitized bilayer graphene. Nature 613, 268–273 (2023). https://doi.org/10.1038/s41586-022-05446-x