Plasmas—hot gases consisting of chaotically-moving electrons, ions, atoms and molecules—comprise the interiors of stars, but scientists can create them artificially using special equipment in the laboratory. If a plasma comes in contact with a solid, such as the wall of the lab equipment, under certain circumstances, the wall is changed fundamentally and permanently: Atoms and molecules from the plasma can be deposited on the solid material, or energetic plasma ions can knock atoms out of the solid, and thereby deform or even destroy its surface. A team from the Institute of Theoretical Physics and Astrophysics at Kiel University (CAU) has now discovered a surprising new effect in which the electronic properties of the solid material, such as its electrical conductivity, can be changed by ion impact in a controlled, extremely fast and reversible manner. Their results were recently published in Physical Review Letters.