Spectroscopy Lab Finds New Property in Quantum Matter

A Johns Hopkins research team has proved that a particular quantum material can demonstrate electrical dipole fluctuations at conditions near -450°F, a theorized but never-before detected property involving irregular oscillations of tiny charged poles on the material.

“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,” says Natalia Drichko, associate research professor in physics at Johns Hopkins University.

Scientists first synthesized the material, called k-(BEDT-TTF)2Hg(SCN)2Br, 20 years ago, deriving it from organic compounds even though it behaves like a metal.

“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,” says Drichko, senior author of a paper on the research published in the journal Science.

Classical physics describes most of the behavior of physical objects we see and experience in everyday life. In classical physics, objects freeze at extremely low temperatures, Drichko says, but in quantum physics, she emphasizes, science that has grown up primarily to describe the behavior of matter and energy at the atomic level and smaller, where there is motion even at frigid temperatures. “That’s one of the major differences between classical and quantum physics that condensed matter physicists are exploring,” she says.

An electrical dipole is a pair of equal but oppositely charged poles separated by some distance. Such dipoles can, for instance, allow a hair to “stick” to a comb through the exchange of static electricity: Tiny dipoles form on the edge of the comb and the edge of the hair.

Drichko’s research team observed the new extreme-low-temperature electrical state of the quantum matter in Drichko’s Raman spectroscopy lab, where the key work was done by graduate student Nora Hassan. Team members shined focused light on a small crystal of the material, employing techniques from other disciplines including chemistry and biology to observe the dipole fluctuations.

The study was possible because of the team’s custom-engineered spectrometer, an instrument that increased the sensitivity of the measurements 100 times, according to Drichko. The unique quantum effect the team found could potentially be used in quantum computing, a type of computing in which information is captured and stored in ways that take advantage of the quantum states of matter.