Columbia Scientists Discover Quantum Trapping of Electron Waves in Metal
Atomic Defects Trap Electron Waves in Metal
Electron waves can become trapped inside a metal even when escape pathways remain open, according to research published on October 22, 2026, in Science, SciTechDaily reported. The finding provides the first experimental evidence of a bound state in the continuum within a metallic material, a phenomenon previously demonstrated using light waves rather than electrons.
The Tech TL;DR:
- Researchers discovered that electron waves can be trapped by quantum interference near atomic defects in the metal Pd5AlI2.
- The observation marks the first time a bound state in the continuum has been detected with electrons inside a metallic material.
- Controlling these trapped electron states could eventually inform the development of high-sensitivity quantum sensors and quantum information processing.
Quantum Interference Generates Electron Trapping in Pd5AlI2
In a standard metal, electrons move freely through the crystal lattice like waves across the sea. However, measurements of the two-dimensional metal Pd5AlI2—developed in the laboratory of Columbia chemist Xavier Roy—revealed that electrons moved much more slowly than expected. Working alongside theoretical physicist Raquel Queiroz and experimental physicists Cory Dean and Aravind Devarakonda, the research team traced this behavior to electron hopping frustration. The atomic structure of the material generates competing paths for electrons to move between atoms, allowing destructive interference to suppress their movement. Scanning and spectroscopy techniques employed by Abhay Pasupathy subsequently detected unexpected patterns and localized electron waves trapped around crystal lattice defects. “Bound electrons shouldn’t occur in a metal, but they do in Pd5AlI2. What we have observed is the first clear evidence of quantum interference trapping a state in a metal,” Raquel Queiroz stated regarding the findings published in Science.
Researchers Seek to Control Electron Traps for Quantum Processing
While the discovery establishes that quantum interference can trap electrons in metals just as it traps light in optical systems, controlling the formation of these states remains a challenge. In the studied material, the electron traps form around defects that arise randomly during crystal growth. Xavier Roy and Abhay Pasupathy are currently investigating methods to deliberately position these defects and govern the resulting interference patterns. Researchers indicate that trapping particles allows for their manipulation, which could eventually contribute to quantum information processing, quantum chemistry, and highly sensitive quantum sensors. The work was supported by funding from the Brown Institute for Basic Sciences, the U.S. National Science Foundation, the Air Force Office of Scientific Research, and the U.S. Department of Energy.