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Scientists in search of quantum breakthroughs subject crystalline materials to sound waves

Sept. 24 (UPI) — To develop the next generation of quantum technologies, scientists need to find materials with unique optical and electrical properties.

Often, when materials are put under stress and strain, they reveal unusual physical properties. But measuring the nanoscale effects of strain isn’t easy.

To aid the search for quantum properties, scientists at the Argonne National Laboratory set out to precisely measure the effects of sound waves on silicon carbide crystal.

Researchers used X-rays to observe the atomic changes triggered by the strain of sound waves passing through the material. The X-rays helped scientists study the behavior of defects, holes where atoms should be, buried deep inside the crystalline material. Defects in crystalline materials often feature unique quantum properties.

The defects in silicon carbide crystal fluoresce naturally, but researchers wanted to find out whether the properties of the defects can be manipulated by strain. In the lab, the team of scientists used stress to induce electrons trapped near the defects to change spin states, and as a result, release energy in the form of photons.

“We wanted to see the coupling between the sound strain and the light response, but to see exactly what the coupling between them is, you need to know both how much strain you’re applying, and how much more optical response you’re getting out,” Argonne nanoscientist Martin Holt said in a news release.

Holt and his research partners used a technique called stroboscopic Bragg diffraction microscopy to observe the effects of stress on the defects from a variety of angles.

“We’re interested in how to manipulate the original spin state with acoustic waves, and how you can spatially map out the mechanics of the strain with X-rays,” said Argonne materials scientist Joseph Heremans.

By synchronizing the frequency of both the sound waves and X-rays being supplied to the silicon carbide crystal, scientists were able to capture detailed images of the local strain in the material’s nanomechanical structures.

“We’re directly imaging sound’s footprint going through this crystal,” Heremans said. “The sound waves cause the lattice to curve, and we can measure exactly how much the lattice curves by going through a specific point of the lattice at a specific point in time.”

Scientists chose to study silicon carbide crystal because the relationship between the dynamic strain and the quantum behavior of the material’s defects is already pretty well understood. Through their experiments, however, scientists were able to showcase their ability to measure the effects of acoustic strain on quantum properties buried deep inside crystals.

The scientists described the novel observation and measurement techniques this week in the journal Nature Communications.

“This technique opens a way for us to figure out the behaviors in a lot of systems in which we don’t have a good analytical prediction of what the relationship should be,” Holt said.

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