Bandwidth-control orbital-selective delocalization of 4f electrons in epitaxial Ce films

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• Yi Wu, Yuan Fang, Peng Li, Zhiguang Xiao, Hao Zheng, Huiqiu Yuan, Chao Cao, Yi-feng Yang& Yang Liu

  
  

The 4f-electron delocalization plays a key role in the low-temperature properties of rare-earth metals and intermetallics, and it is normally realized by the Kondo coupling between 4f and conduction electrons. Due to the large Coulomb repulsion of 4f electrons, the bandwidth-control Mott-type delocalization, commonly observed in d-electron systems, is difficult in 4f-electron systems and remains elusive in spectroscopic experiments. Here we demonstrate that the bandwidth-control orbital-selective delocalization of 4f electrons can be realized in epitaxial Ce films by thermal annealing, which results in a metastable surface phase with reduced layer spacing. The quasiparticle bands exhibit large dispersion with exclusive 4f character near Γ¯$\stackrel{<span\; style="font-size:16px;font-family:"times\; new\; roman";">¯</span>}{\mathrm{<span\; style="font-size:16px;font-family:"times\; new\; roman";">\Gamma </span>}}$ and extend reasonably far below the Fermi energy, which can be explained from the Mott physics. The experimental quasiparticle dispersion agrees well with density-functional theory calculation and also exhibits unusual temperature dependence, which could arise from the delicate interplay between the bandwidth-control Mott physics and the coexisting Kondo hybridization. Our work opens up the opportunity to study the interaction between two well-known localization-delocalization mechanisms in correlation physics, i.e., Kondo vs Mott, which can be important for a fundamental understanding of 4f-electron systems.

Nature Communications 12, 2520 (2021)

The published article is available at https://www.nature.com/articles/s41467-021-22710-2