This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: New research started with a special material that behaves unusually when it's extremely cold—135 degrees below zero Fahrenheit (minus 93 degrees Celsius), close to the most frigid temperature ever recorded in Antarctica—and showed that the unusual behavior could be extended to well above room temperature—up to about 135 F (57 degrees Celsius), close to the highest heat ever measured in Death Valley, California. The base material was a stack of 3-atom-thin sheets made from a compound called tantalum disulfide.
The special behavior is known as the commensurate charge density wave (CCDW). In contrast to the usual disorderly motion of electrons in a metal, the CCDW causes them to move together in a pattern that traces the internal structure of the material. Getting that behavior to persist when it's warm took one surprising step: adding an amino acid—a building block for proteins—called arginine.
The research came from an international collaboration led by investigators at the UCLA College and the California NanoSystems Institute at UCLA (CNSI). The study was published in Nature Chemistry. The combined material was made of repeated vertical stacks with two layers of arginine sandwiched between single layers of tantalum disulfide.
When two other amino acids were combined with tantalum disulfide, neither showed CCDW behavior at room temperature. The researchers found that the arginine molecule fits into the tantalum disulfide's crystal matrix like a puzzle piece. The perfect fit of the amino acid's size and how its electrons are distributed seem to explain its dramatic effect.
Normally, electrons move more or less randomly through a metal and are easily bumped off course by small-scale vibrations caused by ambient heat. The CCDW, based on the counterintuitive rules of the subatomic quantum world, exhibits orderly motion of electrons that instead flow with such distortions to a material's crystal structure. This special behavior could be harnessed in future technologies, but the need for extremely cold temperatures stands in the way.
The researchers first put tantalum disulfide and arginine together in an earlier study that screened more than 50 different carbon-based molecules to see which ones combine with advanced materials. Extending the temperature range for the CCDW was a happy accident revealed in later analysis. The current study compared the material to tantalum disulfide on its own, using a variety of techniques that measure vibrations, electrical flow, temperature changes and atomic structure.
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