ARPES view on surface and bulk hybridization phenomena in the antiferromagnetic Kondo lattice CeRh2Si2

Abstract

The hybridization between localized 4f electrons and itinerant electrons in rare-earth-based materials gives rise to their exotic properties like valence fluctuations, Kondo behaviour, heavy-fermions, or unconventional superconductivity. Here we present an angle-resolved photoemission spectroscopy (ARPES) study of the Kondo lattice antiferromagnet CeRh2Si2, where the surface and bulk Ce-4f spectral responses were clearly resolved. The pronounced 4f 0 peak seen for the Ce terminated surface gets strongly suppressed in the bulk Ce-4f spectra taken from a Si-terminated crystal due to much larger f-d hybridization. Most interestingly, the bulk Ce-4f spectra reveal a fine structure near the Fermi edge reflecting the crystal electric field splitting of the bulk magnetic 4f 15/2 state. This structure presents a clear dispersion upon crossing valence states, providing direct evidence of f-d hybridization. Our findings give precise insight into f-d hybridization penomena and highlight their importance in the antiferromagnetic phases of Kondo lattices.

Crystal electric field in CeRh2Si2 studied with high-resolution resonant inelastic soft x-ray scattering

“…In contrast, the CEF proposed in Ref. [20] with excited levels at 48 meV and 62 meV (red line) which showed good agreement with the data at T = 30 K (see Fig. 1) is not compatible with the excitation spectrum at room temperature, both on the energy loss and the energy gain side.…”

“…However, close to the surface the CEF acting on the 4f site is often modified due to the broken symmetry and the surface relaxation of the crystal lattice. A strong indication for this are the very different CEF splittings 1 , 2 observed with surface sensitive photoemission [20] compared to what is found with bulk sensitive INS [17] or RIXS (see Table I). …”

“…This system shows a very interesting phase diagram with AFM order and unconventional superconductivity in close proximity and therefore attracts a lot of attention [12][13][14][15][16]. However, the CEF schemes reported in the literature are contradictory both in terms of the observed energy splittings as well as the symmetry and the anisotropy of the CEF levels of the 2 F 5/2 multiplet [17][18][19][20], and still under debate despite more than 20 years of investigations. The previously reported CEF splittings are relatively large (up to 50 meV) and well compatible with the resolution achieved in RIXS to date.…”

Hybridization Effects Revealed by Angle-Resolved Photoemission Spectroscopy in Heavy-Fermion Ce2IrIn8*

“…2(e). This enhanced intensity at the Γ point near the Fermi level is actually the tail of Kondo resonance [31]. From the on/off-resonant comparison, we can find that resonant ARPES not only enhances the Ce 4f cross-section due to the 4d-4f transition, but also enhances the background making the other bands fuzzy.…”

Kondo screening and beyond: An x-ray absorption and dichroism study ofCePt5/Pt(111)

“…In this respect, advanced methods of surface science have demonstrated tremendous potential and novel insight in recent years, notably owing to their resolving capabilities in real or reciprocal space in combination with great spectral resolution. Associating findings from surface sensitive experiments to bulk properties of the respective materials may represent a nontrivial task, since relevant interactions are frequently altered in the vicinity of the surface [12][13][14][15][16][17][18] . Technical limitations in applying nonthermal control parameters as well as the unavailability of classical thermodynamic methods or inelastic neutron scattering restrict the possibilities of systematically studying the properties and phase diagrams of systems at surfaces in an analogous manner to bulk materials.…”