How the electronic structure in URu₂Si₂ changes with temperature: A high-resolution Compton scattering study

We have measured directional Compton profiles on the (001) plane in URu₂Si₂ single crystal at several temperatures. Two-dimensional electron occupation number densities (2D-EONDs) were obtained from the profiles through electron momentum reconstruction and Lock–Crisp–West folding analyses. We have also performed band calculations based on 5 f-electron itinerant and localized models and derived theoretical 2D-EONDs for comparison. The experimental 2D-EOND at 300 K is well described by the localized model, and the 2D-EOND at 10 K is consistent with the theoretical one based on the itinerant model. The difference between 2D-EONDs at 30 and 100 K reflects a gradual change in the electronic structure, which reveals some of the crossover phenomena from localized to itinerant states. The change from localized to itinerant states is also reflected in a B(r) function, which is obtained in the reconstruction analysis and is an autocorrelation function of the wave function in the position space. The process by which the electronic structure in URu₂Si₂ changes is demonstrated through a series of experimental results.