Angle-resolved photoemission study of USb2 the 5f band struc(3)

Single crystal antiferromagnetic USb2 was studied at 15K by angle-resolved photoemission with an overall energy resolution of 24 meV. The measurements unambiguously show the dispersion of extremely narrow bands situated near the Fermi level. The peak at th

The PAM model takes into account the coherent nature of electrons, thus, it may better describe the strong correlation of electrons in lattice systems. The complex nature of PAM calculations requires the application of some generalizations such as infinite dimensions, but initial results give certain general conclusions such as smaller temperature dependence of the f-band and its hybridization with conduction states. The PAM models are still generic and unable to calculate a specific strongly correlated system.

Though there are no specific calculations within the PAM for USb2 (or for any element or compound for that matter), general predictions of the models can be assessed by experimental studies. To zero order, the photoemission results require a model which captures the periodicity of the lattice as well as the strong electron-electron interactions.

In principle, the distinction between localized and band-like behavior of f-electrons should be easily observable in PES experiments. However, the expected f-band dispersion is small, which makes the problem challenging to solve in practice. Any reasonable attempt to experimentally evaluate the 5f dispersion and weight needs to exhibit both very good energy and momentum resolution, and needs to take place on high-quality single crystals. The problem is observed in older PES data, where polycrystals measured at resonance (e.g. at photon energy over 100 eV) showed only a broad featureless structure pinned at Fermi edge, the so-called actinide triangle [13].

In the current study of USb2 we have found a narrow feature near Fermi level which clearly exhibits dispersion. Dispersion was also observed in our normal emission photoemission data, giving evidence that USb2, a layered compound, has some 3D character. The f-electron dispersion in the PES limits candidate models to those models which can accommodate periodicity with the lattice for a description of the electronic structure. The narrow feature at the Fermi level presented below is a true band feature with a natural linewidth less than the total dispersion of the feature in reciprocal space. Within this framework, the feature near E F in USb2 is a true band state but renormalized to such an extent that the dispersion and natural linewidth are at least two orders of magnitude smaller than that in free electron models.

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