A longstanding mystery in condensed-matter physics involves the appearance of a 'hidden order' state in URu2Si2 at low temperature — an unexpected phase change that is accompanied by a sharp change in the bulk properties of the material. The problem is related to the appearance of a 'heavy fermion' state. Here, scanning tunnelling microscopy and spectroscopy have been used to image the electronic structure of URu2Si2 at sub-atomic resolution, revealing how the hidden order state evolves with decreasing temperature.
- A. R. Schmidt
- M. H. Hamidian
- J. C. Davis