Physicists Discover Evidence for a New Property of Quantum Matter

Long-theorized molecular interactions finally have proof of existence in quantum materials thanks to a team of researchers from Johns Hopkins University.

Researchers might have cracked a never before discovered property of quantum matter. A team from the Institute for Quantum Matter at Johns Hopkins University proved that certain quantum materials can demonstrate electrical dipole fluctuations. 

These unique movements are irregular oscillations of tiny charged poles on the material. The researchers noted these oscillations occur at extremely cold temperatures -- roughly minus 450 degrees Fahrenheit or lower. 

Physicists Discover Evidence for a New Property of Quantum Matter
Source: JHU/ Science Daily

This particular movement has long been theorized but yet proven until now. The material in question was created over two decades ago and is called k-(BEDT-TTF)2Hg(SCN)2 Br. The material comes from organic compounds; however, it behaves a lot like a metal. 

"What we found with this particular quantum material is that, even at super-cold temperatures, electrical dipoles are still present and fluctuate according to the laws of quantum mechanics," said physicist Natalia Drichko. Drichko serves as an associate research professor in physics at the Johns Hopkins University.

Drichko explained why this particular discovery was important.

"Usually, we think of quantum mechanics as a theory of small things, like atoms, but here we observe that the whole crystal is behaving quantum-mechanically," said Drichko, senior author of a paper on the research published in the journal Science.

Traditional physics and understanding of molecular movement note that as objects freeze, their molecular movement slows to the point of stopping. However, in quantum physics, the motion still remains even at the coldest of temperatures, Drichko explained. "That's one of the major differences between classical and quantum physics that condensed matter physicists are exploring," she said.

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Electrical dipoles are equal but oppositely charged poles separated by a distance. There are three types of dipoles in molecular studies. First, there are permanent dipoles that are two atoms in a molecule with vastly different electronegativity.

In a permanent dipole, one atom will attract electrons more than another, making one substantially more negative and the other more positive. (These are also called polar molecules.) The second type of dipole is instantaneous dipoles that happen by chance when electrons are more concentrated in one area of a molecule.

This creates a temporary dipole. The last type is induced dipoles that happen when one molecule repels another's electrons and sparks a dipole moment in that molecule. The dipoles studied by physicists are the same types that can allow hair to temporarily adhere to a comb via static electricity. Dipoles form on the edge of a comb and attract the hair. 

Drichko's team utilized the Raman spectroscopy lab in order to get the quantum matter at the low temperatures needed to observe the theorized activity. Key work in the lab was conducted by grad student Nora Hassan.

In the lab, Hassan and her fellow researchers focused light onto a crystal of the material. The teams leveraged other techniques found in both chemistry and biology to study these dipole fluctuations. 

The Johns Hopkins team also built a custom spectrometer, a machine 100 times more powerful than traditional lab spectrometers. The research could be used in the development of quantum computing systems, and in developing quantum systems that could work efficiently even at extreme temperatures.