Wigner crystals are exotic phases of matter in which electrons arrange themselves into a regular, crystalline pattern due to their mutual repulsion. This phenomenon occurs at extremely low electron densities and temperatures, where the kinetic energy of the electrons becomes negligible compared to their Coulomb (electrostatic) repulsion.
First predicted by physicist Eugene Wigner in 1934, the idea is that when electrons are sparse and move very slowly (low kinetic energy), they can minimize their total energy by spreading out in space to reduce repulsive interactions. Instead of forming a typical conducting sea of free electrons, they localize into an ordered structure resembling a crystal lattice.
Wigner crystals are challenging to observe because they require conditions where quantum effects dominate and thermal motion is minimal. They have been detected in systems like two-dimensional electron gases in semiconductor heterostructures, on the surface of liquid helium, and in trapped ion systems.
Studying Wigner crystals provides insight into strongly correlated electron systems and quantum phase transitions, and has implications for both fundamental physics and the design of future quantum materials and devices.