Researchers from the University of Washington have achieved a significant breakthrough by imparting graphene-like properties to graphite, a three-dimensional material. This discovery opens up possibilities for modifying other bulk materials to exhibit characteristics similar to their two-dimensional counterparts, potentially expanding the horizons of technological advancements.
Exploring the Potential of Two-Dimensional Materials
For many years, scientists have been investigating the potential of two-dimensional materials, which consist of single layers of atoms, to revolutionize various fields such as computing, communication, and energy. These materials exhibit unique properties due to the limited motion of subatomic particles like electrons in two dimensions. Such “exotic” properties include peculiar forms of magnetism, superconductivity, and collective electron behaviors, all of which hold promise for advancements in computing, communication, energy, and other domains.
Traditionally, researchers believed that these exotic two-dimensional properties were confined to single-layer sheets or short stacks, with bulk versions of these materials displaying different behaviors due to their complex three-dimensional atomic structures.
An Unexpected Breakthrough in Two-Dimensional Materials
Contrary to previous assumptions, a groundbreaking study published in Nature on July 19, led by the University of Washington, demonstrated the possibility of imbuing graphite, a bulk three-dimensional material commonly found in pencils, with properties akin to graphene, its two-dimensional counterpart. The unexpected nature of this breakthrough raises the prospect of exploring whether similar bulk materials can also acquire two-dimensional characteristics. If successful, two-dimensional sheets will not be the sole source for igniting technological revolutions, as bulk three-dimensional materials could be just as valuable.
“Stacking single layer on single layer — or two layers on two layers — has been the focus for unlocking new physics in 2D materials for several years now. In these experimental approaches, that’s where many interesting properties emerge,” explained senior author Matthew Yankowitz, an assistant professor of physics and materials science and engineering at the University of Washington. “But what happens if you keep adding layers? Eventually, it has to stop, right? That’s what intuition suggests. But in this case, intuition is wrong. It’s possible to mix 2D properties into 3D materials.”
Exploring New Physics in Three-Dimensional Materials
The research team, including scholars from Osaka University and the National Institute for Materials Science in Japan, adapted a common method used to manipulate two-dimensional materials. They stacked layers of graphene and graphite together at a small twist angle. By placing a single layer of graphene on top of a thin bulk graphite crystal and introducing a twist angle of approximately 1 degree between them, the researchers discovered novel and unexpected electrical properties not only at the twisted interface but also within the bulk graphite.
The twist angle plays a crucial role in generating these properties. As explained by Yankowitz, who is also affiliated with the UW Clean Energy Institute and the UW Institute for Nano-Engineered Systems, a twist angle between two-dimensional sheets, such as graphene, creates a moiré pattern. This pattern alters the movement of charged particles like electrons and induces exotic properties in the material.
Unprecedented Results and Future Possibilities
In experiments involving graphite and graphene, the twist angle induced a moiré pattern that led to surprising outcomes. The introduction of a twist solely at the graphene-graphite interface caused a change in the electrical properties of the entire graphite material. When a magnetic field was applied, electrons deep within the graphite crystal displayed unusual properties similar to those at the twisted interface. Essentially, the single twisted graphene-graphite interface became integrated with the rest of the bulk graphite.
“Though we were generating the moiré pattern only at the surface of the graphite, the resulting properties were bleeding across the whole crystal,” said co-lead author Dacen Waters, a postdoctoral researcher in physics at the University of Washington.
In the realm of two-dimensional sheets, moiré patterns give rise to properties that could be valuable for quantum computing and other applications. By inducing similar phenomena in three-dimensional materials, new avenues open up for studying unconventional and exotic states of matter, with the potential to bring them from the laboratory to our everyday lives.
“The entire crystal takes on this 2D state,” noted co-lead author Ellis Thompson, a doctoral student in physics at the University of Washington. “This is a fundamentally new way to affect electron behavior in a bulk material.”
Yankowitz and his team believe that their approach of generating a twist angle between graphene and bulk graphite could be extended to create hybrid 2D-3D materials using other substances like tungsten ditelluride and zirconium pentatelluride. This innovative approach could unlock a new method for re-engineering the properties of conventional bulk materials by leveraging a single 2D interface.
“This method could become a truly fertile ground for investigating exciting new physical phenomena in materials with mixed 2D and 3D properties,” added Yankowitz.
Reference: “Mixed-dimensional moire systems of twisted graphitic thin films,” published on July 19, 2023, in Nature.
Co-authors of the paper include Esmeralda Arreguin-Martinez, a graduate student, and Yafei Ren, a postdoctoral researcher, both from the Department of Materials Science and Engineering at the University of Washington. Other co-authors include Ting Cao, an assistant professor of materials science and engineering at the University of Washington; Di Xiao, a professor of physics and chair of materials science and engineering at the University of Washington; Manato Fujimoto from Osaka University; and Kenji Watanabe and Takashi Taniguchi from the National Institute for Materials Science in Japan. The research received funding from various organizations, including the National Science Foundation, the U.S. Department of Energy, the UW Clean Energy Institute, the Office of the Director of National Intelligence, the Japan Science and Technology Agency, the Japan Society for the Promotion of Science, the Japanese Ministry of Education, Culture, Sports, Science and Technology, and the M.J. Murdock Charitable Trust.
- National Science Foundation: DMR-2041972, MRSEC-1719797, DGE-2140004
- U.S. Department of Energy: DE-SC0019443
- Japan Science and Technology Agency: JPMJCR20T3
- Japan Society for the Promotion of Science: JP21J10775, JP23KJ0339, 19H05790, 20H00354, and 21H05233
- Japanese Ministry of Education, Culture, Sports, Science and Technology: JPMXP0112101001
Frequently Asked Questions (FAQs) about Graphite revolution
What is the significance of the University of Washington’s breakthrough in integrating graphene-like properties into graphite?
The breakthrough demonstrates the possibility of imparting two-dimensional (2D) properties to bulk graphite, expanding the potential for technological innovations and challenging previous assumptions about the behavior of 2D materials in three-dimensional (3D) structures.
What are the potential applications of this discovery?
The integration of 2D properties into bulk materials opens up possibilities in various fields such as computing, communication, and energy. The resulting exotic properties, including unique magnetism, superconductivity, and collective electron behaviors, could find applications in quantum computing and other advanced technologies.
How did the researchers achieve this integration of 2D properties in bulk graphite?
The researchers stacked a sheet of graphene onto a bulk graphite crystal at a small twist angle, creating a moiré pattern. This pattern induced unexpected electrical properties not only at the twisted interface but also within the bulk graphite, effectively integrating the 2D properties throughout the material.
Can this approach be extended to other bulk materials?
The researchers believe that their approach could be used to modify other bulk materials, such as tungsten ditelluride and zirconium pentatelluride, to exhibit 2D-like properties. This opens up opportunities for re-engineering the properties of conventional bulk materials using a single 2D interface.
What are the implications of this breakthrough for future research?
The discovery of mixed-dimensional moiré systems in bulk materials provides a new avenue for studying unusual and exotic states of matter. It offers researchers the opportunity to explore exciting new physical phenomena and potentially bring them out of the laboratory and into practical applications.