Mysterious Quantum Properties in Material Point to New Applications in Electronics

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But Philip J.W. Moll, now at the Max Planck Institute for Chemical Physics of Solids in Germany, found a way to minimize this damage and provide finely polished surfaces in the tiny slices using tools at the Molecular Foundry. “Cutting something and at the same time not damaging it are natural opposites. Our team had to push the ion beam fabrication to its limits of low energy and tight beam focus to make this possible.”

When researchers applied an electric current to the samples, they found that electrons race around in circles similar to how they orbit around an atom’s nucleus, but their path passes through both the surface and the bulk of the material.

The applied magnetic field pushes the electrons around the surface. When they reach the same energy and momentum of the bulk electrons, they get pulled by the chirality of the bulk and pushed through to the other surface, repeating this oddly twisting path until they are scattered by material defects.

The experiment represents a successful marriage of theoretical approaches with the right materials and techniques, Analytis said.

“This had been theorized by Andrew Potter on our team and his co-workers, and our experiment marks the first time it was observed,” Analytis said. “It is very unusual—there is no analogous phenomena in any other system. The two surfaces of the material ‘talk’ to each other over large distances due to their chiral nature.”

“We had predicted this behavior as a way to measure the unusual properties expected in these materials, and it was very exciting to see these ideas come to life in real experimental systems,” said Potter, an assistant physics professor at the University of Texas at Austin. “Philip and collaborators made some great innovations to produce extremely thin and high-quality samples, which really made these observations possible for the first time.”

Researchers also learned that disorder in the patterning of the material’s crystal surface doesn’t seem to affect the behavior of electrons there, though disorder in the central material does have an impact on whether the electrons move across the material from one surface to the other.

The motion of the electrons exhibits a dual handedness, with some electrons traveling around the material in one direction and others looping around in an opposite direction.

Researchers are now building on this work in designing new materials for ongoing studies, Analytis said. “We are using techniques normally restricted to the semiconductor industry to make prototype devices from quantum materials.”

Berkeley Lab’s Molecular Foundry and Advanced Light Source are both DOE Office of Science User Facilities.

This work was supported by the Department of Energy’s Office of Science, the Gordon and Betty Moore Foundation, and the Swiss Federal Institute of Technology in Zurich (ETH Zurich).

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