Probing 5f-state configurations in URu2Si2 with U L3-edge resonant x-ray emission spectroscopy

TL;DR

This study uses resonant x-ray emission spectroscopy at the U L3 edge to investigate the 5f electronic configuration in URu2Si2, revealing partial delocalization and stable occupancy across temperatures, informing hidden order theories.

Contribution

It provides the first direct measurement of 5f occupancy and delocalization in URu2Si2 using RXES, challenging localized f2 ground state models.

Findings

5f orbital in URu2Si2 is partially delocalized with nf ≈ 2.87

No significant change in 5f occupancy from 10 K to higher temperatures

Results constrain theoretical models of the hidden order in URu2Si2

Abstract

Resonant x-ray emission spectroscopy (RXES) was employed at the U L3 absorption edge and the La1 emission line to explore the 5f occupancy, nf, and the degree of 5f orbital delocalization in the hidden order compound URu2Si2. By comparing to suitable reference materials such as UF4, UCd11, and alpha-U, we conclude that the 5f orbital in URu2Si2 is at least partially delocalized with nf = 2.87 +/- 0.08, and does not change with temperature down to 10 K within the estimated error. These results place further constraints on theoretical explanations of the hidden order, especially those requiring a localized f2 ground state.