Scientists awaken multiple quantum interactions in a single material

The search and manipulation of novel properties emerging from the quantum nature of matter could lead to next-generation electronics and quantum computers. But finding and designing materials that can host such quantum interactions has proved a difficult task.

"Harmonizing multiple quantum mechanical properties, which often do not coexist together, and trying to do it by design is a highly complex challenge," said Northwestern University's James Rondinelli.

But Rondinelli and an international team of theoretical and computational researchers have now done just that. Not only have they demonstrated that multiple quantum interactions can coexist in a single material, but they have also discovered how an electric field can be used to control these interactions to tune the material's properties.

This breakthrough could lead to ultrafast, low-power electronics and quantum computers that operate much faster than current models in the areas of data acquisition, processing and exchange.

Supported by the US Army Research Office, the National Science Foundation of China, the German Research Foundation and China's National Science Fund for Distinguished Young Scholars, the research is reported in a paper in Nature Communications. James Rondinelli, professor in materials and manufacturing in Northwestern's McCormick School of Engineering, and Cesare Franchini, professor of quantum materials modeling at the University of Vienna in Austria, are the paper's co-corresponding authors.

"The possibility of accessing multiple order phases, which rely on different quantum-mechanical interactions, in the same material is a challenging fundamental issue and imperative for delivering on the promises that quantum information sciences can offer."Cesare Franchini, University of Vienna

Quantum mechanical interactions govern the capability of and speed with which electrons can move through a material. This determines whether a material is a conductor or an insulator. It also controls whether or not the material exhibits ferroelectricity, or shows an electrical polarization.

"The possibility of accessing multiple order phases, which rely on different quantum-mechanical interactions, in the same material is a challenging fundamental issue and imperative for delivering on the promises that quantum information sciences can offer," Franchini said.

Using computational simulations performed at the Vienna Scientific Cluster, the team discovered coexisting quantum-mechanical interactions in the compound silver-bismuth-oxide (Ag₂BiO₃). Bismuth, a post-transition metal, permits the spin of electrons to interact with its own motion – a feature that has no analogy in classical physics. It also does not exhibit inversion symmetry, suggesting that ferroelectricity should exist when the material is an electrical insulator. By applying an electric field to the material, the researchers were able to control whether the electron spins were coupled in pairs (exhibiting Weyl-fermions) or separated (exhibiting Rashba-splitting), as well as whether the system is electrically conductive or not.

"This is the first real case of a topological quantum transition from a ferroelectric insulator to a non-ferroelectric semi-metal," Franchini said. "This is like awakening different kinds of quantum interactions that are quietly sleeping in the same house without knowing each other."

This story is adapted from material from Northwestern University's McCormick School of Engineering, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.