Observation of electronic crystallites in solids

In crystalline solids, electrons are mobile so that one can induce a flow of electrons (current) by applying a bias voltage. In 1930s, Wigner proposed that even electrons can be crystallized or immobilized if repulsion between electrons is storng enough. A crystal made of electrons is not only interesting in itself, but also has been predicted to play a key role in high-temperature superconductivity and superfluidity.

A research team led by Keun Su Kim, Yonsei University and funded by the National Research Foundation of Korea (Leader Grant) reports the first experimental discovery of atomic-scale electronic crystallites in solids (to appear in Nature, October 2024). By angle-resolved photoemission spectroscopy, they measured the energy-momentum relation of electrons doped from alkali metals to the surface of black phosphrous. Whereas the energy-momentum relation must be periodic in crystalline systems, they found a striking aperiodic relation expected for atomic-scale electronic crystallites.

If one likened electrons with long-range crystalline order to a solid state, and those with no crystalline order to a gas state, electronic crystallites with only short-range crystalline order are the electronic analogue of liquid crystals, said Keun Su Kim.

This image shows atomic-scale electronic crystallites (blue balls arranged in a hexagon pattern and connected by white wavy lines) floating in the sea of electrons (dark balls).

[Reference] S. Park et al. Electronic rotons and Wigner crystallites in a two-dimensional dipole liquid, Nature, https://doi.org/10.1038/s41586-024-08045-0

[Main Author] Soobin Park, Keun Su Kim (Yonsei Univeristy)

*Contact email: Professor Keun Su Kim (keunsukim@yonsei.ac.kr)