Two-dimensional materials are revolutionizing solid state physics

It all started with a piece of tape. In 2004, the physicists Andre Geim and Konstantin Novoselov were surprised to discover that they could use it to peel off a few flakes that were just one atom thick from a block of graphite. In this way they had created the first two-dimensional material – although theoretical physicists had declared it impossible. As they experimented with the wafer-thin layer, they realized that its properties were radically different from those of three-dimensional materials. Graphene, as Geim and Novoselov called it, established an entirely new category of matter. Their discovery changed solid state physics. Thousands of researchers also started working on graphene, dreaming of the diverse technologies it could make possible. Geim and Novoselov were awarded the Nobel Prize in Physics in 2010.

That same year, young Columbia University physicist Jie Shan and her colleague Kin Fai Mak saw evidence that two-dimensional layers of molybdenite might be even more extraordinary than graphene. Even to the trained eye, molybdenite looks almost exactly like graphite: a silvery lustrous crystal. Both materials shed flakes suitable for making pencils. But don’t be fooled by these outward appearances. Despite their similarity, the atomic lattices of the substances form completely different worlds for the electrons in them. The Swedish chemist Carl Scheele first discovered this 244 years ago when he immersed both minerals in acids. The garish gas clouds that were created looked anything but the same. So he came to the conclusion that molybdenite must be a new substance. The scientist finally paid for the experiments with his life, he died at the age of 43 from heavy metal poisoning.

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Nevertheless, molybdenite found its way into use: Because it quickly breaks down into powdery fragments, it developed into a popular lubricant over the course of the 20th century. It made skis glide through the snow better and smoothed the exit of bullets from gun barrels. This “flocculation” also makes it possible to obtain two-dimensional layers of the crystal, as in the case of graphite.

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