Origin Of Magic Angles In Twisted Bilayer Graphene
Twisted bilayer graphene has been a hot topic of research in the field of condensed matter physics for several years now. This two-dimensional material consists of two layers of graphene which are rotated with respect to each other, resulting in a moiré pattern. When the angle between the two layers is adjusted to a specific value, a range of novel electronic properties emerge. The most notable of these is the observation of superconductivity at low temperatures, which has the potential to revolutionize the field of electronics. This article will explore the origin of the magic angles in twisted bilayer graphene and their implications for the scientific community.
What Is Twisted Bilayer Graphene?
Graphene is a two-dimensional material made of a single layer of carbon atoms arranged in a hexagonal lattice. It is known for its exceptional mechanical, electrical, and thermal properties. Twisted bilayer graphene, on the other hand, is made of two layers of graphene stacked on top of each other with a small twist angle between them. When the angle is very small, the moiré pattern formed by the overlap of the two lattices is almost uniform. But when the twist angle is adjusted to a specific value, the moiré pattern becomes much larger, and the electronic properties of the material change drastically.
What Are Magic Angles?
The magic angle is the angle at which twisted bilayer graphene exhibits highly unusual electronic properties. It was first discovered by Pablo Jarillo-Herrero and his team at the Massachusetts Institute of Technology (MIT) in 2018. They found that when the twist angle between the two layers of graphene was precisely 1.1 degrees, the material became an insulator at low temperatures. However, when they introduced doping, the material became a superconductor, meaning it could conduct electricity with zero resistance.
Since this discovery, several research groups around the world have been investigating the properties of twisted bilayer graphene at the magic angle. They have found that the material has a host of unique properties, including the ability to exhibit fractional quantum Hall states, spin-polarized currents, and strange metal behavior.
How Do Magic Angles Work?
The magic angle in twisted bilayer graphene is a result of quantum mechanical effects. When the twist angle is adjusted to 1.1 degrees, the electrons in the material become strongly correlated. This means that they interact with each other in very specific ways, leading to the observed electronic properties. The magic angle is thought to result in a flat electronic band, which is responsible for the insulating behavior of the material. However, when the material is doped, the flat band becomes superconducting, leading to the observed superconductivity.
Implications for the Scientific Community
The discovery of magic angles in twisted bilayer graphene has opened up a new area of research in the field of condensed matter physics. Scientists are now investigating the properties of other two-dimensional materials to see if they exhibit similar behavior. This research has the potential to revolutionize the field of electronics, as superconductivity could be used to create highly efficient electronic devices, such as quantum computers.
Furthermore, the discovery of magic angles has important implications for our understanding of quantum mechanics. It provides a unique example of strongly correlated electron behavior, which has been predicted by theory but has been difficult to observe experimentally. The study of magic angles in twisted bilayer graphene is helping to shed light on the fundamental properties of matter and could lead to a better understanding of the universe as a whole.
Conclusion
The discovery of magic angles in twisted bilayer graphene has been a major breakthrough in the field of condensed matter physics. This two-dimensional material exhibits a range of novel electronic properties, including superconductivity, when the twist angle between the layers is adjusted to a specific value. The research on magic angles has the potential to revolutionize the field of electronics and provide important insights into the nature of matter and the universe. As scientists continue to study this fascinating material, we can expect to see many more exciting discoveries in the years to come.
