Researchers have achieved unprecedented properties by changing the stacking of atoms.
Scientists from the Massachusetts Institute of Technology (MIT) have made significant progress in materials science, transforming ordinary graphite into a material with new, previously unobserved properties. By isolating five ultra-thin layers of graphite and arranging them in a specific order, the researchers were able to customize the material so that it exhibits three important qualities that are not found in the natural state of this material.
"It's like a one-stop shop," notes Long Zhu, an assistant professor in the MIT Department of Physics and lead author of the study, whose results were published in the journal Nature Nanotechnology on October 5. "Nature is full of surprises, and we didn't even know that graphite could hide so many interesting things."
The research gave an impetus to the development of a new direction in physics, known as"twistronics". Graphite consists of graphene-single-layer sheets of carbon arranged in a honeycomb-like structure. Graphene has attracted considerable attention from scientists since its discovery about 20 years ago. About five years ago, an MIT team discovered that stacking individual sheets of graphene at a small angle to each other gives the material new properties, from superconductivity to magnetism.
In the new study, Zhu and his colleagues found interesting properties of the material without any twisting. They found that five layers of graphene stacked in a certain sequence allow electrons to interact with each other, which creates conditions for the manifestation of new properties.
To isolate the new material, called the graphene pentalayer rhombohedral stack, a new type of microscope developed by Zhu at MIT in 2021 was used. This tool allows you to quickly and economically determine various characteristics of materials at the nanoscale.
Using this microscope, the scientists searched for multi-layered graphene with a very precise stacking pattern known as rhombohedral. "There are more than 10 possible styling options when going to five layers, and the rhombohedral is just one of them," Zhu says.
Once the required sequence of layers was determined, the researchers integrated the electrodes into a microscopic structure consisting of a protective layer of boron nitride covering ultra-thin five-layer rhombohedral graphene. This allowed them to manipulate the electrical characteristics of the material by changing the voltage. Experiments have shown that, depending on the applied voltage, the material can exhibit insulating, magnetic, or topological properties.
"We found that the material can be an insulator, magnetic or topological," Zhu says. Topological materials allow electrons to move freely along the edges of the material, but not through its middle, making the edge of the material an ideal conductor, and the center an insulator.
"Our work establishes rhombohedrally stacked multilayer graphene as a highly customizable platform for exploring new opportunities in highly correlated and topological physics," Zhu and his co-authors conclude in Nature Nanotechnology.
Scientists from the Massachusetts Institute of Technology (MIT) have made significant progress in materials science, transforming ordinary graphite into a material with new, previously unobserved properties. By isolating five ultra-thin layers of graphite and arranging them in a specific order, the researchers were able to customize the material so that it exhibits three important qualities that are not found in the natural state of this material.
"It's like a one-stop shop," notes Long Zhu, an assistant professor in the MIT Department of Physics and lead author of the study, whose results were published in the journal Nature Nanotechnology on October 5. "Nature is full of surprises, and we didn't even know that graphite could hide so many interesting things."
The research gave an impetus to the development of a new direction in physics, known as"twistronics". Graphite consists of graphene-single-layer sheets of carbon arranged in a honeycomb-like structure. Graphene has attracted considerable attention from scientists since its discovery about 20 years ago. About five years ago, an MIT team discovered that stacking individual sheets of graphene at a small angle to each other gives the material new properties, from superconductivity to magnetism.
In the new study, Zhu and his colleagues found interesting properties of the material without any twisting. They found that five layers of graphene stacked in a certain sequence allow electrons to interact with each other, which creates conditions for the manifestation of new properties.
To isolate the new material, called the graphene pentalayer rhombohedral stack, a new type of microscope developed by Zhu at MIT in 2021 was used. This tool allows you to quickly and economically determine various characteristics of materials at the nanoscale.
Using this microscope, the scientists searched for multi-layered graphene with a very precise stacking pattern known as rhombohedral. "There are more than 10 possible styling options when going to five layers, and the rhombohedral is just one of them," Zhu says.
Once the required sequence of layers was determined, the researchers integrated the electrodes into a microscopic structure consisting of a protective layer of boron nitride covering ultra-thin five-layer rhombohedral graphene. This allowed them to manipulate the electrical characteristics of the material by changing the voltage. Experiments have shown that, depending on the applied voltage, the material can exhibit insulating, magnetic, or topological properties.
"We found that the material can be an insulator, magnetic or topological," Zhu says. Topological materials allow electrons to move freely along the edges of the material, but not through its middle, making the edge of the material an ideal conductor, and the center an insulator.
"Our work establishes rhombohedrally stacked multilayer graphene as a highly customizable platform for exploring new opportunities in highly correlated and topological physics," Zhu and his co-authors conclude in Nature Nanotechnology.
