STM study of the atomic and electronic structure of a single-layer Kondo lattice CePt₆/Pt(111)

While bulk CePt₅ shows antiferromagnetic order below 1 K, a multi-layered thin film of CePt₅ grown on a Pt(111) substrate exhibits heavy-fermion behavior below 20 K[1]. However, the growth of single layer CePt₅ has been controversial as summarized in Ref.[2] and spectroscopic studies for the electronic states of the single layer are still lacking. In this work, we study the structure and electronic states of 1 unit layer (u.l.) of a Ce-Pt intermetallic compound on Pt(111) using scanning tunneling microscopy/spectroscopy (STM/STS)[3]. By depositing Ce atoms onto Pt(111) and subsequent annealing, an ordered (2×2) structure was observed, which is reproduced by a structural model of 1 u.l. CePt₆/Pt(111) consisting of a topmost Pt₄ layer and an underneath CePt₂ layer. By measuring STS spectra and quasiparticle interference, we found that an onset energy of the surface state observed on Pt(111) shifts downward on the surface Pt₄ layer of the 1 u.l. CePt₆ due to charge transfer from the CePt₂ layer. We discuss possible two-dimensional coherent Kondo effect with the observed STS spectra on the 1 u.l. CePt₆.

[1] M. Klein et al., Phys. Rev. Lett. 106, 186407 (2011)

[2] J. Kemmer et al., Phys. Rev. B 90, 195401 (2014).

[3] K. Ienaga et al., Phys. Rev. B (accepted)