Abstract
Previous high-resolution angle-resolved photoemission (ARPES) studies of URu2Si2 have characterized the temperature-dependent behavior of narrow-band states close to the Fermi level (E F) 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 global k-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 2p core-levels, x-ray polarization, surface-dosing modification, and theoretical surface slab calculations are employed to assist identification of bulk versus surface state character of the E F-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, Z and X points, incommensurate 0.6a* nested Fermi-edge states located along Z–N–Z are found to be distinctly different from the DFT FS prediction. The temperature evolution of these states above T HO, combined with a more detailed theoretical investigation of this region, suggests a key role of the N-point in the hidden order transition.
Highlights
Bulk band theory predicts a shallow electron pocket at the X point that compensates for the charge imbalance of the Fermi surface (FS) electron-sheets at Γ and hole-sheets at Z
We have given an overview of past angle-resolved photoemission (ARPES) results for the photon energy regimes of Fig. 1(c) and presented new results for the less studied intermediate low photon energy regime of 30-150 eV
The identification of non-bulk surface states, essential for achieving the ultimate goal of determining the bulk electronic structure, is made from this comparison of the two surface terminations assisted by response to surface modifications, and by comparison to bulk and surface slab theory calculations
Summary
For an ARPES k-space navigation guide, figure 1(c) provides a schematic of many bct BZs stacked along the (001) direction illustrating different photon energy ranges measured in the literature and in this study. Both - and - plane BZ stacking are represented, and a 14 eV inner potential barrier at the surface is used to convert the measured Fermi-edge kinetic energies into the kz values inside the crystal. We provide discussion of ordered phase zone-folding, heavy mass origins, the itinerant versus localized debate, nesting vectors, FS gapping and pseudogaps, as they relate to this newly identified N-point region that has rich potential for explanation of the hidden order phenomena
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