Distinct spin and orbital dynamics in Sr2RuO4
Our results highlight the Hund metal nature of Sr2RuO4 and provide key information for the understanding of its unconventional superconductivity.
![Resonant x-ray scattering from the square-lattice compound Sr2RuO4 (left) yields detailed maps of electronic excitations as a function of energy E and momentum Q (right).](/8131616/original-1699546422.jpg?t=eyJ3aWR0aCI6MjQ2LCJvYmpfaWQiOjgxMzE2MTZ9--cfa027884dbe4ae721293e2486e28020bc6cfea9)
Conduction electrons in quantum materials form delocalized states that can be quantum-coherent over macroscopic length scales, while being subject to local interactions akin to those in atomic physics. This dichotomy spawns a large variety of collective quantum phenomena and remains one of the major challenges of modern condensed matter physics.
The square-lattice compound Sr2RuO4 has long served as a model system for the influence of atomic-scale correlations on the macroscopic electronic properties – including particularly the unconventional superconducting state that forms at low temperatures. Momentum-space maps acquired with a high-resolution x-ray spectrometer have now revealed a separation of energy scales for spin and orbital correlations, which can be attributed to interactions akin to Hund’s rules in atomic physics. The results serve as a testbed for state-of-the-art many-body theories and yield fresh insight into the origin of superconductivity in Sr2RuO4.