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.
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.