What are 2D materials and why are they of interest to scientists?

If you’ve read about quantum research recently, in Columbia News or elsewhere, you may have heard the term 2D or two-dimensional materials.

An illustration of the atomic structure of graphene, an ultra-strong 2D form of carbon.

In January, Columbia chemists published a study on the first 2D heavy Fermion, a class of materials containing very heavy electrons. In November, the engineering school published an article on “Laser control of a 2D material.” And earlier last year, researchers discovered both superconductivity and ferroelectricity in the same 2D material. The list goes on.

So, what are 2D materials and why are scientists so interested in them?

Two-dimensional materials are exactly what they sound like: materials that are only one or two atoms thick but are wider in every other direction. Often, the 2D materials scientists work with are a few square micrometers in size – invisible to the naked eye, but visible with the kind of microscope you might have used in high school science class. The 2D materials scientists work with are a mix of natural materials, like graphene, a super-strong form of carbon discovered at Columbia in 2004, and lab-synthesized materials, like CeSil, a crystal first assembled in Columbia last year. composed of cerium, silicon and iodine. These materials usually start out in three dimensions, and scientists break them down into two dimensions to conduct experiments on them and discover what physical properties, like superconductivity or magnetism, might appear when the materials are atomically flat. Scientists are working to develop new ways to create 2D materials from scratch, without needing to separate them from 3D, but the quality of these is still imperfect.

There are many things that make 2D materials interesting, but the main one is that they limit how particles such as electrons can move inside them. Xavier Roy, a chemist from Colombia used a trafficking analogy to explain:

“Think of it like this: if we had flying cars that could travel in three-dimensional space, we would be able to reduce most of the traffic in New York. But because our current cars can only travel in two dimensions, we end up with huge traffic jams in Times Square,” Roy said in a recent interview.

“The same thing happens for electrons when we move from 3D to 2D, but in our case the “traffic” between electrons is beneficial! As these electron-electron interactions become stronger, we can completely change the properties of a material. For example, as the thickness of 3D heavy fermion materials is reduced (i.e., as they become more two-dimensional), they can transition from magnetic to superconducting.

Two-dimensional materials can also be relatively easily modified: stacking them with slight angles between layers, applying forces such as electric fields and magnetic fields, and stretching the materials by twisting or applying pressure can change their properties. Let’s take just one example: By simply stacking two sheets of a material called tungsten diselenide on top of each other, twisting them, and adding or removing an electrical charge, the material can change from a conductive metal to electricity to an insulator blocking the electricity and back.

Scientists are also excited about the potential uses of 2D materials in technology, which scientists often call “applications.”

Two-dimensional materials will likely play a critical role in the next generation of electronics, including quantum computers still under development. For what? Largely because 2D materials are ultra-small with unique, controllable properties (like superconductivity), and technology is always looking for something that achieves results faster, more efficiently and more efficiently. using less space.

Source: Columbia University