The degree of 5f electron localization in URu2Si2: electron energy-loss spectroscopy and spin-orbit sum rule analysis

TL;DR

This study investigates the localization of 5f electrons in URu2Si2 using electron energy-loss spectroscopy and spin-orbit sum rule analysis, revealing partial localization and intermediate coupling, which impacts understanding of its hidden order state.

Contribution

It provides the first detailed analysis of 5f electron localization in URu2Si2 using spin-orbit sum rules, comparing it with other uranium compounds and clarifying the electron coupling mechanism.

Findings

URu2Si2's 5f electrons are more localized than in other uranium metals.

Intermediate coupling is the appropriate model for URu2Si2's 5f electrons.

Localization degree influences the hidden order state and Fermi surface contributions.

Abstract

We examine the degree of 5f electron localization in URu2Si2 using spin-orbit sum rule analysis of the U N4,5 (4d \to 5f) edge. When compared to {\alpha}-U metal, US, USe, and UTe, which have increasing localization of the 5f states, we find that the 5f states of URu2Si2 are more localized, although not entirely. Spin-orbit analysis shows that intermediate coupling is the correct angular momentum coupling mechanism for URu2Si2 when the 5f electron count is between 2.6 and 2.8. These results have direct ramifications for theoretical assessment of the hidden order state of URu2Si2, where the degree of localization of the 5f electrons and their contribution to the Fermi surface are critical.