A team of physicists from the Massachusetts Institute of Technology (MIT) has discovered a property of graphene that could transform the world of superconductivity and magnetism, opening the doors to the development of more efficient and faster electronic devices, new types of extremely sensitive sensors , or even the possibility of quantum computers based on graphene.
The discovery , published in the prestigious journal Nature Nanotechnology , reflects the skill of manipulating matter at an almost atomic scale , being not only a testament to human ingenuity, but also pointing to a new horizon for materials science.
By isolating five sheets of graphene and stacking them in a specific order , MIT researchers have created a material with properties that defy the natural characteristics of the known material.
Let’s now see how they have done it and what the possibilities are for the future of electronics and quantum physics.
What is graphite
Let’s start by better understanding what graphite is , an allotrope of carbon that occurs in nature with a hexagonal crystalline structure with a series of notable physical properties.
It is made up of layers of carbon atoms arranged in a honeycomb pattern, each layer is known as graphene. These layers are held together by weak Van der Waals forces , allowing them to slide over each other, which explains the lubricity of graphite. This linked arrangement of its atoms gives it high electrical conductivity in the plane of the layers, but a much lower conductivity in the perpendicular direction.
First isolated in 2004, graphene , as I mentioned before, is essentially a single sheet of carbon atoms from graphite, with a thickness of a single atom . This two-dimensionality gives graphene a set of exceptional properties. It is extremely strong, being about 200 times stronger than steel, and at the same time it is remarkably light. It is also one of the most flexible materials known, capable of stretching up to 20% of its original size without breaking. Its thermal and electrical conductivity is outstanding, surpassing even metals traditionally known for these characteristics, such as copper.
Over the past few years it has inspired an avalanche of research and development, with applications ranging from flexible electronics and touch screens to advanced composites for the aerospace industry and biomaterials for medical applications.
The impact of graphene and related materials has been so significant that the 2010 Nobel Prize in Physics was awarded for the insulation of graphene.
Spinning graphene on graphene is a good idea
The concept of ” twistronics ” originates from the term ” twist “, which means twist, and refers to the manipulation of the relative angle between layers of two-dimensional materials, such as graphene . This technique has revolutionized materials research by allowing control of electronic properties through precise tuning of the twist angle between overlapping layers of graphene. The “magic” of twistronics lies in the ability to alter the electronic states and the interactions between them, simply by changing the angle between the graphene layers, without altering the chemical composition of the material.
In this way several discoveries have been made. One of them is the fact that by adjusting the layers to about 1.1 degrees, the system can behave like a superconductor, that is, conduct electricity without resistance. This phenomenon was surprising because graphene, in its isolated form, is not a superconductor. Another notable advance is the discovery of Mott insulating states in spun graphene systems, where, despite the presence of charge carriers, the material acts as an insulator due to strong interactions between electrons.
Advances in this regard are not only fascinating for theoretical physicists; They also have potential practical implications . For example, the ability to induce and control superconductivity in two-dimensional materials could be revolutionary for quantum information technology and cryptography. On the other hand, materials with tunable properties could be key in the development of advanced sensors, photonic devices and more efficient energy storage systems.
The new discovery: no need to turn
And so we come to the recent discovery, where scientists have managed to promote remarkable electronic properties without resorting to twisting the graphene layers. In particular, attention has been focused on the rhombohedral stacking of five layers of graphene , demonstrating that manipulation of the stacking structure itself can be as powerful as twisting in modifying electronic properties.
By stacking, rather than spinning, the phenomenon of electronic correlation has occurred, so that the interaction between electrons is so strong that they cannot be described as independent particles. In graphene this phenomenon has been magnified due to its particular arrangement of atoms and electronic orbitals.
This discovery has immense potential in electronics and spintronics, since materials with high electronic correlations can be used to develop devices that require high energy efficiency or to create systems that exhibit rapidly changing properties, such as resistive memory for next generation computing.
How did they achieve it?
MIT has used the s-SNOM (scattering-type Scanning Near-field Optical Microscope), a device with innovative technology that represents a significant advance in researchers’ ability to observe and characterize materials at the nanometric level. s-SNOM takes advantage of the interaction between light and surface nanostructures to overcome the resolution limits imposed by traditional optical microscopes, which are restricted by the principle of diffraction.
In this case, they have taken advantage of the ability of the s-SNOM microscope to identify the rhombohedral stacking order of graphene , thus making it possible to visualize and confirm the presence of the properties described above.
The use of s-SNOM has opened new avenues in the research of two-dimensional materials and complex heterostructures . Its application has been essential not only in the identification of stacking structures, but also in the understanding of physical phenomena such as insulation due to strong interaction between electrons and the possibility of unconventional superconductivity.