In a metal, electrons usually glide freely, like waves across the sea. But in the new material Pd₅AlI₂, quantum electron waves have suddenly found themselves locked in place — for the first time in history.
Researchers from Columbia University in the United States published the result on 22 October 2026 in the journal Science. The team, led by theoretical physicist Raquel Queiroz and chemist Xavier Roy, together with experimentalists Cory Dean, Abhay Pasupathy and Arvind Devarakonda, worked with two-dimensional layers of the new metal Pd₅AlI₂. The scientists noticed that electrons in this material move more slowly than usual. In atomic-resolution spectroscopy, clear images of bound electron waves appeared near defects in the crystal lattice.
Ordinary metals conduct current because electrons move freely. Here, however, atoms and orbitals create competing paths for electrons to "hop." These paths cancel each other out — destructive interference arises. As a result, an electron wave cannot leave its point, even though a continuous sea of other waves stretches around it. This is a bound state in the continuum — a BIC.
Imagine two waves on water meeting and completely cancelling each other out: at the meeting point a calm surface remains, even though all around it is still churning. This is exactly how quantum interference holds an electron wave in a metal, even though classically it should have escaped.
Previously, such states had been observed only for light in specially etched structures. Now, for the first time, they have been observed for electrons in a metal. This opens the way to creating quantum sensors, improving information transfer in quantum computers, and developing new approaches in quantum chemistry. For now, the traps arise randomly near defects, but scientists are already looking for ways to place them deliberately at desired points.
The results, published in Science on 22 October 2026, confirm that electronic BICs are real and explicable by the same quantum mechanics as optical ones.
Physicists now have a new recipe for finding metals in which electron waves can be deliberately locked up and manipulated.
