Probing the electronic structure of $\mathrm{UTe}_2$ with ARPES and high-energy spectroscopy

Abstract

$\mathrm{UTe}_2$ has emerged as one of the most intensively studied strongly correlated materials in recent years owing to its unconventional superconductivity and the possible realization of a spin-triplet, topologically nontrivial pairing state. A central open issue concerns the nature of the $\mathrm{U}\,5f$ electrons and their participation in low-energy quasiparticle states. In this review, we summarize recent spectroscopic studies of $\mathrm{UTe}_2$ using momentum-resolved angle-resolved photoemission spectroscopy (ARPES) and element- and configuration-sensitive X-ray probes, including X-ray absorption spectroscopy (XAS), X-ray absorption near-edge structure (XANES), X-ray magnetic circular dichroism (XMCD), resonant X-ray emission spectroscopy (RXES), and resonant inelastic X-ray scattering (RIXS). A key finding is the pronounced technique dependence of the inferred electronic structure. We synthesize the present spectroscopic picture by integrating these results with modern electronic-structure calculations such as density functional theory plus dynamical mean-field theory (DFT+DMFT). These findings support an intermediate-valence ground state with significant admixture of $5f^2$ and $5f^3$ configurations in $\mathrm{UTe}_2$, and they delineate key experimental and theoretical benchmarks needed to connect the normal-state electronic structure to the superconducting mechanism.