From hidden to large-moment-antiferromagnetic order in URu2Si2: an x-ray study of 5f occupation and wave function symmetry.

• Applicant: Dr. Andrea Severing
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 387555779

In many fascinating U intermetallic compounds, the intricate interplay of band formation and electron correlation effects of the U 5f electrons is an intellectual challenge that has not yet been mastered. The question is, should the modelling start with band theory or a local atomic approach? This has been particularly troublesome because neither the presence nor the symmetry of the active atomic-like states was so far experimentally accessible nor are there generally accepted numbers for the filling of the 5f shell. With state-of-the-art synchrotron spectroscopy, we have shown that multiplets persist not only in the hidden order compound URu2Si2; they even persist in an itinerant, Pauli paramagnetic compound like UFe2Si2 thus overturning the 30-year-old wisdom that band structure will do the job. We rather show, that these bands must be strongly renormalized due to the remnant local aspects. The follow-up project shall therefore not only include further spectroscopy investigations (NIXS, HAXPES, ARPES), in addition DFT(LDA)+DMFT calculations shall be performed for a quantitative description of the U compound’s electronic structure.

• DFG Programme: Research Grants