Ren Zhang

A drop of ink in a glass of water quickly spreads, tinting the whole liquid. Similarly, electrons in a metal move freely, like molecules in a gas. But when a magnetic impurity, an atom with its own magnetic moment, enters this medium, something strange happens.

Imagine a long corridor with many doors that open and close in a strict rhythm. If you send sound down it, the echo from each door will distort the melody, and a crooked wall at the end will throw off the entire rhythm. It would seem that understanding what's happening deep inside is now impossible. But there's a trick.