Wavy Atomic Layers Enable Unusual Superconducting Properties

New Material with Wavy Atomic Layers Shows Unusual Superconducting Properties

MIT physicists, along with collaborators, have developed a new material with unique superconducting and metallic properties. This material consists of wavy atomic layers that are only billionths of a meter thick and repeat over a large sample, making it easier to manipulate and explore its quantum behavior. The ability to work with such a large sample is significant because it simplifies the study of interactions at the atomic level that give rise to its unusual properties.

Reported in *Nature*, this breakthrough material was created through rational design, meaning its development was guided by a deep understanding of material science and chemistry. This approach gives the team confidence that they can engineer more materials with novel properties. While other materials also form wavy atomic structures, this new one is considered the most flawless, with perfectly uniform layers across the entire crystal.

2D Materials and the Moiré Superlattice

Two-dimensional materials, which consist of only a few atomic layers, are intriguing to physicists because they can exhibit unique properties. By slightly twisting these layers, a pattern called a moiré superlattice can emerge, leading to effects such as superconductivity and unconventional magnetism. However, moiré materials are challenging to create and study due to their small size.

The MIT team has been working on creating materials that exhibit similar properties but are easier to manipulate. In their process, they mix powders, heat them in a furnace, and let chemical reactions naturally form large macroscopic crystals.

New Superconducting Material

The new material is made up of thin metallic layers of tantalum and sulfur, stacked with spacer layers composed of strontium, tantalum, and sulfur. This structure repeats over thousands of layers, forming a large crystal. The waves in the atomic layers arise from a mismatch in the size and structure of the crystal lattices of the different layers, causing one layer to buckle.

These tiny waves are key to the material’s superconducting properties. At certain temperatures, it allows electrons to flow with no resistance, but this superconductivity is affected by the waves, making it stronger in some areas and weaker in others. The material also has unusual metallic properties, as electrons move more easily along the troughs of the waves than over the peaks.

This new wavy structure has drastically altered the behavior of the material, giving the electrons a preferred direction of flow. The researchers believe this discovery opens the door to numerous applications and the creation of an entirely new family of materials with uncharted properties and exciting possibilities.