New materials with wavy layers of atoms exhibit unusual superconducting properties

Physicists at MIT and colleagues have created a new material with unusual superconducting and metallic properties, thanks to wavy layers of atoms only billions of meters thick that repeat themselves over and over again to create a sample macroscopic that can be used manually. The large size of the sample makes it very easy to probe its quantum behavior, or the interactions at the atomic scale that produce its properties.

Work, reported on Natureit is also important because the goods were made logically. In other words, the material recipe is based on the team’s understanding of the physical properties and chemistry of this family of materials. As a result, physicists hope to create even more new materials with unusual properties.

Furthermore, although there are other materials that create wavy atomic structures, the team believes that this is the most perfect. The nanoscopic waves are uniform throughout the crystal, which is made up of thousands of layers of zinc.

“Such materials go beyond what one would imagine in a crystal—observing and understanding how new physical properties can emerge is an exciting opportunity,” says Joseph Checkelsky, senior researcher at the project and Associate Professor of Physics at MIT.

2D tools

Two-dimensional materials, or materials with only one or a few layers of atoms, have attracted the attention of physicists because they can be used to produce materials with new, unusual properties. For example, rotating, or twisting, one or more layers at a small angle creates a unique pattern called a moiré superlattice that can produce phenomena including superconductivity and unusual magnetism.

But moiré materials are difficult to make—they have to be assembled by hand—and difficult to study because of their atomic size. Checkelsky’s team has been working to create a uniform and easy-to-use product.

“We basically mix powders of material, expose them to temperatures of a few hundred degrees Celsius in an oven, and rely on chemical reactions” to form large crystals that with properties dictated by atomic interactions. “That’s a significant achievement,” says Aravind Devarakonda, MIT Ph.D., now an assistant professor at Columbia University. Devarakonda is the current first author Nature paper.

In 2020, Checkelsky and several colleagues in the current work reported the first such data generated in this way in a journal. Science. The paper was accompanied by an opinion piece by Professor Leslie M. Schoop of Princeton University.

In 2021, Checkelsky and colleagues explained to Nature the physics behind how that material can exhibit two different types of superconductivity. The new wavy material is the second member of this family of compounds.

Like a layer cake

Like the wafer, the new material is made of atomically thin layers of tantalum and sulfur packed on a spacer layer made of strontium, tantalum and sulfur. This structure repeats itself over thousands of units to form a large crystal.

Devarakonda and colleagues believe that the waves arise from mismatches in the size and shape of each crystal layer. Similarly, one layer—made of tantalum and sulfur—comes into place on top of the other, forming a wave. Imagine placing legal paper on top of regular printing paper. In order for legal paper to fit on top of plain paper, some paper will need to be glued to the top. The new format is similar, except that the legal paper is sometimes “folded” into the regular paper, creating waves.

Unusual things

Those small waves, on the other hand, are behind interesting material things. For example, at a certain temperature the material can become superconducting, where electrons travel through the material without resistance.

In this case, “electronics are printed by structural methods [waves]”Devarakonda says. In other words, “superconductivity also takes this form of depression. In some areas it is strong, and in other areas it is weak.”

Likewise, the material has unusual metallic properties. That’s because electrons find it much easier to go down the channels of the wave—or down the valley—rather than up and over the hills of the wave.

“So what we’ve done is give the electrons a direction. It’s easy for them to flow from one direction to another,” Devarakonda says. “We showed that by producing [wave] shape we can greatly change the behavior of the membrane. We have planted a flag; now we and others can run with requests. By standing on the shoulders of giants, we have created a new family of products. It’s a completely unknown place that has brought unexpected results, and surprises are always nice. “

In addition to Devarakonda and Checkelsky, the paper’s authors are Alan Chen, a graduate student in MIT’s Department of Electrical Engineering and Computer Science; Shiang Fang, formerly a postdoctoral researcher at MIT’s Department of Physics, now at Google Deepmind; David Graf of the National High Magnetic Field Laboratory; Markus Kriener of the RIKEN Center for Emergent Matter Science in Japan; Austin J. Akey of Harvard University; David C. Bell of Harvard; and Takehito Suzuki of Toho University.