A thin film of neodymium nickelate is a layer just fifteen nanometers thick, thousands of times thinner than a human hair. At low temperature it doesn't conduct current, because electrons are locked in place. But hit it with a laser pulse lasting 30 femtoseconds, that is, 30 millionths of a billionth of a second, and it suddenly starts conducting current like a metal wire.
It used to be thought that conductivity and atomic order change together, like two wheels of the same cart. This experiment showed that the wheels can spin separately. Electrons start moving freely, while atoms stay in their places. It's as if a dancer changed tempo but not pose: the legs move faster, while the torso stays frozen.
To completely rearrange the atomic pattern, you need a far more powerful laser pulse. The transition to a metal requires an energy of 0.64 millijoules per square centimeter, while changing the shape of the lattice takes 2.3 millijoules. That's a difference of almost four times. This discovery could help create ultrafast switches that are controlled by light and don't waste energy on rearranging atoms.
The transition temperature of NdNiO3 is about 180 K, only slightly above the boiling point of liquid nitrogen (77 K), so a standard cryostat is enough to observe the effect.
The idea of a material that changes its conductivity while keeping its crystal structure recalls the concept of 'phase transitions without a change of shape' from science fiction, for example in Isaac Asimov's novel The Gods Themselves, where a substance can switch to a state with different properties without visible changes.