Imagine a tiny highway where electrons can only travel in one direction, with no exits or turns allowed. Scientists at Penn State and Saint Louis University have just created a special material that makes this possible — and it could help us build computers and devices that work in completely new ways.
The researchers built something called a quantum anomalous Hall insulator, or QAH insulator for short. It's made from extremely thin layers of a material called bismuth antimony telluride, grown at Penn State's two-dimensional crystal consortium facility. What makes this material special is its behavior: while electricity can't flow through the center of the material, it easily travels along the edges in a single, clockwise direction — like a one-way street with no intersections.
This might sound simple, but it actually lets scientists study something called non-Hermitian physics, which deals with systems that behave in unusual ways not explained by ordinary physics rules. One of those unusual behaviors is called the non-Hermitian skin effect, where quantum states — the tiny building blocks that determine a material's properties — bunch up near one edge instead of spreading out evenly.
"We wanted to show that these phenomena can emerge naturally in a quantum material," said Morteza Kayyalha, an assistant professor of electrical engineering at Penn State who led the research. "Our work lays the groundwork for achieving scalable, non-Hermitian behavior with a quantum material platform rather than relying only on optical or circuit-based designs."
A key advantage of this new platform is that the material doesn't need external magnetic fields to work once it's been magnetized. Traditional devices that study these unusual behaviors typically require such fields during operation, making them more complex and harder to scale up. The team's QAH insulator sidesteps this problem entirely.
The researchers built ring-shaped devices with electrical contacts placed around the perimeter. By measuring how signals traveled between contacts, they reconstructed what scientists call a conductance network — essentially a map showing how electricity moves through the material. Comparing these measurements with theoretical models, they found that the material's behavior matched predictions from the Hatano-Nelson model, a standard framework for identifying non-Hermitian physics.
The findings, published in the journal Science Advances, could eventually help power devices that transport and group electrical signals in ways that traditional electronics cannot achieve. Instead of needing specially designed optical systems or engineered circuits, scientists might one day use these quantum materials as simpler, more practical platforms for exploring new electronic phenomena.