A new ultra-fast laser technique has yielded insights into how iron arsenide materials evolve to form a superconducting state. This transformation involves complex changes in magnetism, structural order, and electronic order that appear to be going on simultaneously — not simply competing with each other. Only by looking at very fast time scales (10 thousandths of a billionth of a second) and using the highest quality single crystals could these transformational changes be separated and analyzed; ultra-fast spectroscopy enabled scientists to study the superconducting transformation dynamics to unravel what happens where and when. The results demonstrated that the crossover involves an independent electronically-driven order (so-called nematic order), previously proposed. These findings will motivate the development of new microscopic theories to further understand this emerging behavior and its influence on superconductivity in these complex materials.
Ultrafast Observation of Critical Nematic Fluctuations and Giant Magnetoelastic Coupling in Iron