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Abstract We report evidence of a finite density of states at the Fermi level at the surface of epitaxial thin films of the narrow bandgap Mott insulator Sr3Ir2O7(001). The Brillouin zone critical points for Sr3Ir2O7(001) thin films have been determined by a comparison of the band mapping from angle-resolved photoemission spectroscopy and low energy electron diffraction. Angle-resolved x-ray photoemission studies reveal the surface termination of Sr3Ir2O7(001) is Sr–O. The absence of dispersion with photon energy, or changing wave vector along the surface normal, indicates the two-dimensional character of the bands contributing to the density of states close to the Fermi level for Sr3Ir2O7(001) thin films. Thus, the finite density of states at the Fermi level is attributed to surface states or surface resonances. The appearance of a finite density of states at the Fermi level is consistent with the increased conductivity with decreasing film thickness for ultrathin Sr3Ir2O7(001) films.
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Global perspectives of the bulk electronic structure of URu 2 Si 2 from angle-resolved photoemission
Abstract Previous high-resolution angle-resolved photoemission (ARPES) studies of URu2Si2have characterized the temperature-dependent behavior of narrow-band states close to the Fermi level (EF) at low photon energies near the zone center, with an emphasis on electronic reconstruction due to Brillouin zone folding. A substantial challenge to a proper description is that these states interact with other hole-band states that are generally absent from bulk-sensitive soft x-ray ARPES measurements. Here we provide a more globalk-space context for the presence of such states and their relation to the bulk Fermi surface (FS) topology using synchrotron-based wide-angle and photon energy-dependent ARPES mapping of the electronic structure using photon energies intermediate between the low-energy regime and the high-energy soft x-ray regime. Small-spot spatial dependence,f-resonant photoemission, Si 2pcore-levels, x-ray polarization, surface-dosing modification, and theoretical surface slab calculations are employed to assist identification of bulk versus surface state character of theEF-crossing bands and their relation to specific U- or Si-terminations of the cleaved surface. The bulk FS topology is critically compared to density functional theory (DFT) and to dynamical mean field theory calculations. In addition to clarifying some aspects of the previously measured high symmetry Γ,ZandXpoints, incommensurate 0.6a* nested Fermi-edge states located alongZ–N–Zare found to be distinctly different from the DFT FS prediction. The temperature evolution of these states aboveTHO, combined with a more detailed theoretical investigation of this region, suggests a key role of theN-point in the hidden order transition.
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- PAR ID:
- 10361749
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Electronic Structure
- Volume:
- 4
- Issue:
- 1
- ISSN:
- 2516-1075
- Page Range / eLocation ID:
- Article No. 013001
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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