Squeezing an Electron Crystal

The Wigner crystal is an elusive beast. Predicted in 1934, this crystal of electrons, which is one of the most strongly correlated states of matter, forms when the electron density is ultralow. But a lack of clean enough systems with that property make it hard to measure. Within the last few months, researchers have imaged its structure. Now another group, led by Vikram Deshpande at the University of Utah, Salt Lake City, has measured the energy required to add an electron to the crystal, a quantity that reveals the interaction strength of the system. Deshpande says that they were happily surprised to finally achieve the result, as it comes after decades of inconclusive measurements by other groups.