E. Guziewicz

Dispersion in the Mott insulator UO2: A comparison of photoemission spectroscopy and screened hybrid density functional theory

We present a comparison between the screened hybrid density functional theory of Heyd, Scuseria, and Enzerhof (HSE06) and high‐resolution photoemission (PES) measurement on a single crystal of UO2. Angle‐resolved photoemission data show a slight dispersion in the f‐orbital derived bands in good agreement with the HSE band structure. The effect of spin‐orbit coupling on the HSE band gap has also been calculated and found to be negligible.

Observation of a kink in the dispersion of f-electrons

Strong interactions in correlated electron systems may result in the formation of heavy quasiparticles that exhibit kinks in their dispersion relation. Spectral weight is incoherently shifted away from the Fermi energy, but Luttingers theorem requires the Fermi volume to remain constant. Our angle-resolved photoemission study of USb2 reveals a kink in a noncrossing 5f band, representing the first experimental observation of a kink structure in f-electron systems. The kink energy scale of 21 meV and the ultra-small peak width of 3 meV are observed. We propose the novel mechanism of renormalization of a point-like Fermi surface, and that Luttingers theorem remains applicable.

Unusual quasiparticle renormalizations from angle resolved photoemission on USb2

Angle-resolved photoemission experiments have been performed on USb2, and very narrow quasiparticle peaks have been observed in a band, which local spin-density approximation (LSDA) predicts to osculate the Fermi energy. The observed band is found to be depressed by 17 meV below the Fermi energy. Furthermore, the inferred quasiparticle dispersion relation for this band exhibits a kink at an energy of about 23 meV below the Fermi energy. The kink is not found in LSDA calculations and, therefore, is attributable to a change in the quasiparticle mass renormalization by a factor of approximately 2. The existence of a kink in the quasiparticle dispersion relation of a band that does not cross the Fermi energy is unprecedented. The kink in the quasiparticle dispersion relation is attributed to the effect of the interband self-energy, involving transitions from the osculating band into a band that does cross the Fermi energy.

Electronic Structure of PuCoGa 5 and UCoGa 5

The electronic structure of the Pu-based superconductor PuCoGa 5 and the Pauli paramagnet UCoGa 5 is investigated using photoemission spectroscopy. The photoemission data of PuCoGa 5 reveal features at the Fermi energy EF and about 1-1.5 eV below EF indicative of itinerant and localized f-electrons, respectively. Angle-resolved spectra of UCoGa 5 show two peaks at similar energies that are highly dispersive, providing evidence for itinerant character of the f-electrons in this material. A comparison of the PuCoGa 5 and UCoGa 5 data to the spectra of α-Pu and δ-Pu serves to place PuCoGa 5 within the context of the more general electronic structure problem in elemental Pu.