Researchers in the US have observed bound states in the continuum in a solid material for the first time. Using a 2D metal developed at Columbia University, they found electrons trapped at defects not by energy barriers but by their own waves cancelling each other out — confirmed with scanning tunnelling microscopy.
In normal metals, free electrons can move anywhere. These trapped states sit inside that free-electron continuum without touching it, something quantum theory predicted but no one had seen in a solid. They could let researchers simulate exotic many-body physics and may one day inform fields like catalysis.
✦ Sometimes electrons are held in place not by walls, but by their own waves.