In a breakthrough that reshapes our understanding of quantum materials, an international team of physicists has finally solved a decades-old mystery about how certain materials suddenly lose their ability to conduct electricity. The answer lies in an elusive quantum phenomenon known as a polaron — a quasiparticle formed when an electron becomes tightly coupled to the vibrations of the surrounding crystal lattice. This subtle “dance” between electrons and atoms can transform a good conductor into a perfect insulator.
The discovery, made by researchers from Kiel University and the DESY research center in Germany, including Professor Kai Rossnagel and Dr. Chul-Hee Min, provides the first direct evidence of polarons in a rare-earth compound composed of thulium, selenium, and tellurium (TmSe1–x Tex). Their findings, published in Physical Review Letters, illuminate one of quantum physics’ most puzzling phenomena: how subtle atomic vibrations can “kill” electrical conductivity.