UTe2: A narrow-band superconductor

Abstract

We investigate the nature of the 5f electrons in the unconventional odd-parity superconductor UTe2, focusing on the degree of covalency, localization versus itinerancy, and dominant electronic configuration. This is achieved using density functional theory (DFT) in combination with dynamical mean-field theory (DMFT) calculations. A key aspect of our approach is the material-specific tuning of the double-counting correction parameter, μdc, within the DFT+DMFT part. This tuning is guided by the energy dependence of photoionization cross sections in valence band photoelectron spectroscopy. The reliability of the parameters is confirmed by the accurate reproduction of the angle-resolved valence-band photoemission spectra and the U4f core-level data. The DFT+DMFT model reveals that in UTe2 U5fn configurations with n=1–4 contribute to the ground state, with the 5f2 configuration being most prevalent and an average 5f shell filling close to 2.5. The model further suggests that the 5f electrons form narrow bands and that charge fluctuations due to degeneracy play a role in addition to coherent valence dynamics arising from hybridization with the conduction bath. Additionally, the significance of the U6d states in UTe2 is discussed.

Source-reported materials — not catalogue approval

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